Indian mariners had first use of magnetic navigational compasses.

Indian mariners had first use of magnetic navigational compasses.

by tonytran2015 (Melbourne, Australia).

Click here for a full, up to date ORIGINAL ARTICLE and to help fighting the stealing of readers’ traffic.

(Blog No. 163).

The magnetic navigational compasses may have been first used by Indian people and may not have been first invented by Chinese people as often claimed.

#compass, #navigation, #lodestone, #Chinese compass, #Olmec magnetic, #Indian, #yantra, #matsya yantra, #maccha yantra,

Indian mariners had first use of magnetic navigational compasses.

1. Claims that China invented the compasses.

Wikipedia said that

“The first compasses were made of lodestone, a naturally magnetized ore of iron, in Han dynasty China between 300 and 200 BC.”[1]

The entry on Han Dynasty said that

“The Han dynasty (/hɑːn/; Chinese: 漢朝; pinyin: Hàn cháo) was the second imperial dynasty of China (206 BC–220 AD).” [2]

Figure: Han Dynasy, from https://commons.m.wikimedia.org/wiki/File:Han_Dynasty_Plain_map.PNG#mw-jump-to-license

So the compasses are used in China after 206 BC, but it was initially only for geomancy.

“The magnetic compass was not, at first, used for navigation, but for geomancy and fortune-telling by the Chinese. The earliest Chinese magnetic compasses were possibly used to order and harmonize buildings in accordance with the geomantic principles of feng shui.” [1]

“The compass was later used for navigation by the Song Dynasty”[1]. (Song Dynasty: Chinese: 宋朝; pinyin: Sòng cháo; 960–1279)

So the written records on the use of compasses for navigation in China are made after year 960 CE.

Note that there were South-pointing chariots used in ancient China before year 235 CE [2b, 2c, 2d] but their operation was not based on magnetism. Their operation relied on the differential between the numbers of rotations of the left and right wheels (of same size) of each chariot to give its total yawing angle since departure.

Those chariots may have even been “first constructed by the Duke of Zhou (beginning of the 1st millennium BC) as a means of conducting homewards certain envoys who had arrived from a great distance beyond the frontiers.” [2b].

Figure: Model of a Chinese South Pointing Chariot, an early navigational device using a differential gear. Original file from
https://commons.m.wikimedia.org/wiki/File:South-pointing_chariot_(Science_Museum_model).jpg#mw-jump-to-license
by Author Andy Dingley, licensed under the Creative Commons Attribution 3.0 Unported license.

2. Appropriate places to look for records.

Many people look for easily read records. China certainly has many records which have been translated into English and are easily understood by readers in the World.

However, China is a land conquering empire, requiring little use of compasses while India is a sea faring trading empire which may benefit a lot from compasses. The logical place to look for records of first use of navigational compasses should therefore be India, an outreaching seafaring trading empire (as necessity is the mother of inventions). Indian influence is obvious over the vast area of Indian Ocean, Polynesian nations and (mostly South) Pacific Ocean [2e].

Any discovery of earlier use of magnetic navigational compass predating Chinese use should not surprise/disappoint investigators as the people of the trading Olmec nation (on the side of the Gulf of Mexico) has even used lodestones, hematite, magnetite since 1500 BC, one thousand year before any record of Chinese first use of lodestones [3], [4].

It is to be noted that China is on the East of India while Arab countries, Spain, Olmec are spread to its West.

3. Many evidences pointing to ancient use of compasses by Indian people .

The literature of the out reaching, sea faring nation India have many evidence to support its first use of the magnetic navigation compass.

“The compass was first used in India, around 1800 BC, for Navigational purposes and was known as “Matsya yantra” (which roughly translates to fish machine) because of the placement of a metallic fish in a cup of oil.” [5]

However, no evidence have been given in [5] to support the claim of “around 1800 BC”.

Reference [6] stated that
“In the Tamil nautical books, the use of compass is mentioned in the fourth century BC”,

4. Evidence on knowledge of magnetic attraction by Indian people since 500BC.

K. V. Ramakrishna Rao [7] pointed out that:

In Vedas, there is reference to “ayas” implying Iron and “Akarshan” attaction, thus, pointing to Iron-magnet relationship.[7]

Kanada (c.550 BCE) mentions about a needle that moves towards a magnet as –

“Manigamanam sucyabhi sarpanam drastakaranam” (Kanadasutra.V.I.15). In the commentary called the Upaskara, the passage has been clearly explained to signify that the needle goes towards the magnet.[7]. (Wikipedia [8] stated that Kanada was estimated to live between 6th and 2nd century BC.)

Kalidasa (c.500 BCE) records: “Siva’s mind has been fixed steadily because of penance. And therefore, now try to distract his attention just like an iron piece is attracted or drawn towards a magnet (ayaskantena lohavat akarshtum)” (Kumarasambavam.II.59).“[7]

The date of 500 BCE assigned for Kalidasa quoted by [7] may be in error. Wikipedia [9] stated that Kalidasa’s works cannot be dated with precision, but they were most likely authored within the 4th-5th century CE. In any event, it is not important, only the date of 550BCE assigned to Kanada is pivotal to the thesis of this article.

5. Evidence on compass use by Indian people since 500CE.

Milindapanho (VII.2.16) composed during 4th-5th centuries CE, mentions about an instrument used by the pilot of a ship for steering the ship.

“And again, O King, as the pilot put a seal on the steering apparatus, lest any one should touch it”.
“[7]

Rhys Davis translates the term as “steering apparatus” and it Sanskrit it is “yantra”, a mechanical devise, just like “matsya yantra” working on mechanical and accompanied with other principles.[7]

Mookerji points out a compass on one of the ships in which Hindus of the early Christian era sailed out to colonize Java and other islands in the Indian ocean. The Hindu compass was an iron fish (called in Sanskrit matsya-yantra or fish machine). It floated in a vessel of oil and point to the north (History of Indian Shipping, London, 1912) [7].

The following is what Mr. J.L. Reid, who was a member of the Institute of Naval Architects and Shipbuilders in England, has said in the Bombay Gazetteer, vol. xiii., Part ii., Appendix A.

“The early Hindu astrologers are said to have used the magnet, in fixing the North and East, in laying foundations, and other religious ceremonies. The Hindu compass was an iron fish that floated in a vessel of oil and pointed to the North. The fact of this older Hindu compass seems placed beyond doubt by the Sanskrit word Maccha Yantra, or fish machine, which Molesworth gives as a name for the mariner’s compass”. [10]

6. Conclusions

The thesis of this article is Indian mariners have already used magnetic navigation compass at least since 500 CE while Chinese had recorded usage of them only after 900 CE, a long four hundred years later.

It appears that the out reaching Indian seafarers had the first use of magnetic navigational compasses. Since necessity is the mother of inventions, it is natural to expect this as India had been an ancient seafaring trading nation.

References:

[1]. https://en.m.wikipedia.org/wiki/History_of_the_compass

[2]. https://en.m.wikipedia.org/wiki/Han_dynasty

[2b]. Needham, Joseph (1986). Science and Civilization in China: Volume 4, Part 2. Taipei: Caves Books, Ltd., pages 286, 289, 291, 298.

[2c]. https://en.m.wikipedia.org/wiki/South-pointing_chariot

[2d]. https://vi.m.wikipedia.org/wiki/Xe_ch%E1%BB%89_nam

[2e]. https://en.m.wikipedia.org/wiki/Tamils

OLMEC LODESTONES

[3]. https://en.m.wikipedia.org/wiki/Olmecs

[4]. https://misfitsandheroes.wordpress.com/2018/01/15/fat-boys-magnetism-and-magic/

INDIAN COMPASSES

[5]. .https://knowledge4civil.wordpress.com/2017/07/23/types-and-uses-of-compass/

[6]. http://www.whoinvent.com/who-invented-the-compass/

[7]. http://archive.worldhistoria.com/compass-in-india_topic17077.html

[6b]. https://en.wikipedia.org/wiki/Kanada_(philosopher)

[6c]. https://en.wikipedia.org/wiki/K%C4%81lid%C4%81sa

[10]. http://www.crystalinks.com/indiaships.html

[11]. http://bharatuntoldstory.tumblr.com/post/73862258619/maccha-yantra-the-ancient-indian-mariners

Added after 2019 Dec 24:

[12]. https://sea.mashable.com/science/8195/singapore-was-possibly-ruled-by-the-indian-chola-dynasty-1000-years-ago-australian-researcher-says

 

RELATED Survival Blogs

Finding north with a lensatic compass, posted August 21, 2017,

How to Blogs

Rice as emergency food., posted December 24, 2016, Mung Beans as grains for self-reliance. , Dried sweet fruits as energy food ,

Latest Social Issues Blogs
, , , ,

divider43.jpg

polymeraust100dollars

Click here for my other blogs on SURVIVAL

SUBSCRIPTION: [RSS – Posts], [RSS – Comments]

MENU: [Contents][Blog Image of Contents ][Archives ] [About]

Blog image of Contents of Survival sub-page

These are the contents of SURVIVAL sub-page re-organized in book order for coherent reading.

Blog image of this page

NAVIGATION (Celestial).

The Sun, the Moon and identifiable stars are used to work out North direction and time in this section.

divider43.jpg

Finding accurate directions by a watch .. Posted on May 12, 2015.. This is my novel technique.

WatchCompass_22NL

Finding accurate directions using a watch, posted on May 19, 2015 . This is my novel technique to replace the horizontal watch method.

DirectionBySun_12N

Caution in finding North by bisector line of a horizontal watch. Posted on October 28, 2015: The commonly known “Scout method” using a horizontal watch may give directional errors of up to 180 degrees in some circumstances.

wpid-bisectorns2c.jpg
, posted on 2018 July 10

Find North By Fingers
, posted on May 06, 2015 . <<<—This is my MOST USEFUL novel technique.

wpid-dividermwp3e2c2.jpg

find North by the Sun

CloudyL

Finding North direction and time using the hidden Sun via the Moon . Posted on July 6, 2015This is a useful technique.

image

Finding North direction and time accurately from the horn line of the Moon. Posted on August 12, 2015. This is my novel technique.

image

Finding North direction and time using the Moon surface features. Posted on July 1, 2015. This is a useful technique.

image

, posted on

Finding North and time by stars. Posted on August 28, 2015

Sky map Northern 3/4 sphere

Sky map Southern 3/4 sphere

Finding North and time with unclear sky. Posted on October 17, 2015. This includes my novel method for finding North and with unclear sky.

image

image

posted on October 21, 2016

ariessmallc30.jpg

. Posted on May 25, 2016

mercator8gc30.jpg

. Posted on April 05, 2018

star map mercatorx1p6

. Posted on April 12, 2018

. Posted on May 13, 2018

. Posted on September 16, 2018

Find North with Orion Equatorial stars

, posted November 3, 2016

slide-sky-disk

Slide Sky-Map for displaying tropical stars, posted on October 7, 2016

photo

, posted July 22, 2016

DirectionTimeByStars

Finding time to Sunset with bare hands. Posted on November 11, 2015 .This is my novel improvement for improved accuracy.

wpid-sunset2.jpg

Finding time to Sunrise with star maps, Posted on January 9, 2016 . This is a novel application for star-maps.

sunrise

Finding direction, distance and navigating to a distant base by stars (Part 1). Posted on January 27, 2016 . This is a novel application for direction of stars in the sky.

Sky map Northern 3/4 sphere

Sky map Southern 3/4 sphere

Finding direction, distance and navigating to a distant base by stars, fine reading of latitude (Part 2).. Posted on February 6, 2016. This is a novel way of accurately arriving at any chosen destination latitude using no instrument.

BStarsN20Vega8C2.jpg

NAVIGATION using only constellations.

The Orion constellation., posted December 26, 2016

The Scorpius constellation, posted on January 8, 2017

The Southern Cross Pointer stars, posted February 26, 2018

NAVIGATION (Terrestrial).

Measuring angles and distances for outdoor survival, posted on June 29, 2016

DistPole

NAVIGATION (Instrumental).

Finding North with a lensatic compass, posted on August 21, 2017

Compass-Magnetic

Determining local magnetic declination by a magnetic compass, posted on March 31, 2016

Compass-Magnetic

, posted on June 14, 2016

compass Reversal

Selecting and using magnetic compasses, posted on July 9, 2016

Compass Lensatic Jap

Shadow stick navigation and graph of solar paths, posted August 19, 2016

ShadowStick

Using GPS in off-grid situations, posted December 06, 2016

Adding longitude and latitude lines to a map, posted August 23, 2017

Map w Coordinates

Navigating with an AM MW radio receiver, posted January 17, 2017

radio sony

Finding North direction and time using geological features, plants and animals, posted August 04, 2017

FIRE MAKING.

Making fire and lighting cigarettes with sunlight. Posted on February 27, 2016

StormWatchDiagram

Quick fire making using sunlight, posted on January 4, 2017

20161222_131508gballfirec60.jpg

Mirror for making fire using sunlight., posted on April 13, 2016

20160105_143215C

Predicting-the-temperature-of-a-habitat, posted on August 31, 2017

compass thermometer

, posted October 23, 2018

Pushing away

FOOD

Rice as emergency food., posted December 24, 2016

20161230_192839ricegrains2c60.jpg

Dried-sweet-fruits-as-energy-food, posted December 24, 2017

Air-grown-mung-bean-sprouts-for-food, posted March 07, 2016

MISCELLANEOUS

Old maps:

Interesting maps of old Saigon , posted on March 20, 2016 .

SaigonThanhQuy

Detecting Counterfeit Currency

Detecting Counterfeit Currency, US dollars, posted on July 15, 2016

Hologram

, posted on November 15, 2016

polymer 5 dollars transparent stripe

Cashless bartering

Cashless-bartering-for-survival, posted on February 20, 2017

crystalball2c70.jpg

Other languages:

Survival-topics-available-in-other-languages , posted on june 18, 2017 .

click to go to polymeraust100dollarsMONEY , 20160105_145215CHOW TO , 20160105_145215CSOCIAL ISSUES , 20160105_145215CLIVING sub-pages

END.

SUBSCRIPTION: [RSS – Posts], [RSS – Comments]

MENU: [Contents][Blog Image of Contents ][Archives ] [About]

Finding accurate direction by a watch

Method for finding accurate directions by a common analogue watch.

by tonytran2015 (Melbourne, Australia).

Click here for a full, up to date ORIGINAL ARTICLE and to help fighting the stealing of readers’ traffic.

(Blog No.120).

WatchCompass_22NL

#find North, #finding North, #compass, #direction, #by Sun, #bisector, #using watch, #with watch, #tilted watch, #inclined watch, #navigation, #without compass

This method uses a common 12-hour watch with analogue face for finding directions. Unlike the traditional method of using the hour hand of a flat lying watch, my method uses a watch tilted from the vertical and gives better accuracy for both North and South hemispheres including tropical zones. When applied to the arctic and antarctic regions, the watch is tilted by more than 67 degrees and lies almost flat on the ground; it becomes the traditional method using flat lying watch.
This method use the position of the Sun, time and known latitude angle to determine directions and Sun declination (therefore estimation of current month of the year).
The method for Northern latitudes is described below.

Method for Northern latitudes.

DirectionBySun_12N

The red line is the bisector. The line CB is drawn on a card representing the half-plane to enable accurate alignment to the Sun

WatchCompass_22NL

The bisector is in the opposite direction of a corresponding 24 hr hand on a 24 hr dial

watchcompassJ

Figure: Summary of finding North by a watch. Red hand is the bisector of 0 hr direction and the hour hand; green hand is its reflection across the (6-12) axis. Axis C-BN for Northern hemisphere is parallel to red hand at equinox days and is (raised above)/(dipped below) the watch dial by 23 degrees at local summer/winter solstice. Axis C-BS for Southern hemisphere is parallel to green hand at equinox days and is (raised above)/(dipped below) the watch dial by 23 degrees at local summer/winter solstice. Green drawing marks are for Southern hemisphere and are the mirror reflection of red drawing marks.

Method for Southern latitudes.

Red hand is the bisector of 0 hr direction and the hour hand; green hand is the reflection of red hand across the (6-12) axis.

In the southern hemisphere points the green hand instead of the red hand.
No ambiguity in equatorial latitudes.
The watch is placed almost vertically in equatorial latitudes by both methods. Methods for both Northern and Southern latitudes gives exactly the same outcomes.

Extension application for both hemispheres.

Figure: Summary of finding North by a watch.

RELATED SURVIVAL BLOGS (Added in December 2016)

Caution in finding North by bisector line of a horizontal watch. Posted on October 28, 2015

Finding directions and time using the Sun and a divider., posted on May 6, 2015. <<<—This is my MOST USEFUL novel technique.

wpid-dividermwp3e2c2.jpg

find North by the Sun

Finding North direction and time using the hidden Sun via the Moon . Posted on July 6, 2015

Finding North direction and time accurately from the horn line of the Moon. Posted on August 12, 2015. This is my novel technique.

wpid-wp-1439376905855.jpeg

Finding North direction and time using the Moon surface features. Posted on July 1, 2015.

wpid-wp-1435755781395.jpeg

, posted on Circumpolar Stars Nth

Finding North and time by stars. Posted on August 28, 2015

Finding North and time with unclear sky. Posted on October 17, 2015.

wpid-bstarsn20b.jpg

, posted July 22, 2016

NorthByKnownStar

Click here for my other blogs on divider43.jpgSURVIVAL

Click here go to Divider63D400 Home Page (Navigation-Survival-How To-Money).

SUBSCRIPTION: [RSS – Posts], [RSS – Comments]

MENU: [Contents][Blog Image of Contents ][Archives ] [About]

 

Finding North with a lensatic compass

Finding North with a lensatic compass

by tonytran2015 (Melbourne, Australia).

Click here for a full, up to date ORIGINAL ARTICLE and to help fighting the stealing of readers’ traffic.

(Blog No.76).

#find North, #finding North, #compass, #lensatic, #magnetic, #true North.

Finding North with a lensatic compass.

A magnetic compass uses the local magnetic field generated by the rotating core of the earth to give the rotational axis of the earth. The two directions are reasonably close.

The magnetic compass is a secondary directional instrument to people who can observe celestial bodies for navigation but is a primary practical directional instrument to people who work under the forrest canopy or underground and cannot observe any Celestial body. (Gyro-compasses are too expensive for most people).

This blog shows how to use lensatic compasses to their full capability.

1. Basic operation (working with Magnetic and True Norths).

Magnetic Declination

Figure: True North, Magnetic North and Magnetic Deviation.

Obtain the magnetic deviation for your area. This deviation is commonly between (-45) degrees and +45 degrees and it slowly changes to a new value every year. The deviation is obtainable from the internet or by the method given in reference [2]. Positive magnetic declination means the Magnetic North is on the East of True North.

If you are using a compass with a rotating compass rose which always points to magnetic North, just read the graduation on the card and ADD the signed magnetic declination to it.

2. Using a lensatic compass

A lensatic compass provides a small lens to read the heading of the compass from a rotating rose.

Compass lensatic

Figure 1: An old ex-US Army lockable dry compass (made around 1965, initially known as M-1950 compass) from disposal stores remains robust and can keep on working although the clear glass has become partially clouded. The lid is open by 70 degrees..

Compass lensatic 2

Figure 2: A lensatic compass with the lid open to vertical postion (90 degrees).

Compass Lensatic 3

Figure 3: A lensatic compass with the lid open by 135 degrees.

Compass Jap. lensatic

Figure 4: A lensatic compass with the lid open by 180 degrees.

The steps are:

1. Open the lid by 90 degrees to its vertical position. The lid has an aiming slit with a sighting wire.

2. Open the small sighting tab with the lenses by 90 degrees to vertical posotion. This also unlock the compass rose of the M-1950 compass.

3. Place your thumb through the ring to keep the compass vertically on top of your hand.

4. Place your sighting eye behind the lens to see the scale on the rose and the target point simultaneously. The sighting tab may have to move closer or away from the scale to produce a clear reading.

5, When the slit on the sighting tab, the wire on the lid and the target all line up, the figure on the rose gives the target direction relative to magnetic North on the rose.

6. Add the SIGNED magnetic declination to it to get the direction relative to TRUE North.

3. Reconnect to true North.

When using a magnetic compass, form the habit of reconnecting the true North given by the compass to the true North given by the Sun, the Moon, terrain, landmarks, etc… This prevents many possible disasters.

find North by watch

Figure: Cross checking directions with those from a Celestial method whenever possible is a desirable habit. This illustration is from reference [7].

find North by the Sun

Figure: Cross checking directions with those from a Celestial method whenever possible is a desirable habit. This illustration is from reference [4].

4. Precaution against magnetic anomalies .

Besides magnetic deviation caused by the core of the earth, there are also deviations near ground surface caused by man-made objects and ore bodies. These are called “Magnetic Anomalies”. An anomaly produces non-parallel magnetic field lines and non-constant magnetic field strength.

The following steps help to detect any magnetic non-uniformity in order to detect such anomalies and to avoid disorientation when using a magnetic compass (A magneto-meter is better for this detection as it supplies the extra accurate value of field strength but it requires batteries.).

1/- Count the yaw and pitch oscillation frequencies of the needle of any new compass. Write them on a piece of paper for future reference.

2/- Check the polarity and the yaw and pitch frequencies before packing the compass for any trip. If the frequencies have decreased the needle may have lost part of its magnetism and re-magnetization may be needed.

3/- Have a habit of cross checking directions with those from Celestial methods (given in references [4,5,6,7]) whenever the Sun or the Moon or bright stars can be seen. The cross checking with the direction determined by the method given in [7] also verifies that your watch is still working.

4/- Frequently take the bearing of your destination in both standing and crouching/sitting positions (with different heights), even if you are confident of your current position. This ensures that your compass is ready when needed and you are prepared against any sudden loss of visibility (due to change in weather, terrain, falling down a crevice! . . .). Any quick change in magnetic direction with height or with horizontal travel distance usually reveals a very strong, meter-scaled magnetic anomaly. The anomalies may be caused by buried metal objects (steel-reinforced bunkers, car bodies, tank bodies, unexploded bomb-shells!, magnetic ores,…) or even induced magnetic field from high voltage power lines.

5/- If anomaly is suspected, count the yawing frequency of the needle. The external field strength acting on the needle is proportional to the square of this frequency. For example, if the frequency goes up by 2, the external magnetic field strength may have gone up by 4.

6/- Distant objects such as mountain peaks, light houses, transmission towers can help detecting the sudden change in magnetic deviation when you travel. The magnetic bearings of these distant objects should only change slowly. If there is any sudden change in their bearings you may have to check the accuracy of your compass or the change in magnetic deviation.

Notes:

Compasses are usually NOT suitable for rail travelers as the carriage bodies and the rails underneath it creates magnetic abnormality.

Compasses mounted in cars and boats have special, additional compensaring devive to eliminate the influence by the car or boat bodies.

5. A special mode of operation to reduce own influence.

Compass lensatic away from body

Figure 3: Hand posture for holding type M-1950 compass for sighting with a stretched arm. The finger through the brass ring is the middle finger. The sighting is carried out using the slit in the sighting tab and the wire in the lid. The lens has no function in this sighting mode. This is my own novel mode of operation not designed by the makers of type M-1950 compasses.

Magnetic material carried on users’ bodies can affect the readings on their compasses. They have to use the following mode of operarion to reduce that effect.

Using the lockable compasses.

Any tilt tolerant, lockable compass can also be used in this mode. Tilt tolerance ensures that the needle can point North before the lock is engaged to freeze it in place. The ex_US Army compass (model M-1950) in figure 1 of Step 2 can be used in this mode, and is surprisingly accurate, as it is tilt tolerant and the inertia of its rotating compass rose ensures that the needle orientation is retained while the lock is engaging. A lockable M-1950 compass is used in the following way (This is my own novel mode of operation, not designed by the makers of type M-1950 compasses. Do NOT complain to them that their compasses are not comfortable to use in this way!) :

Place the lid and the sighting tab of the M-1950 compass in vertical positions to have the compass in unlocked and operating condition. Turn the holding ring near the sighting tab fully downward. Curl the middle finger of your hand and stick it through the holding ring of the compass. Grip the compass by pressing the end of the index finger against the lid hinge and the joint of the thumb against the sighting hinge. Stretch your arm while holding the lensatic compass horizontally level at the height of our eyes, away from your head, with its lid vertical and its lock still fully disengaged (sighting tab in vertical position).

Take aim of the destination by the aiming guide then hold till for 3 seconds. Gently engage the lock (push the sighting tab into horizontal position) by only raising only the first joint of your thumb to push against the bend of the sighting tab while keeping the rest of the body motionless. After having been locked, the whole compass is bought to your comfortable reading distance to read the locked position of the needle. The magnetic bearing of the aiming line is the value on the compass rose at the point nearest to the hinge. It is hard to read but is definitely readable even with the sighting tab fully down.

Please leave any comments and suggestions here so that the posting can be improved !!

References.

[1]. tonytran2015, Beware of perilous flips by magnetic compasses, survivaltricks.wordpress.com, , posted on June 14, 2016.

[2]. tonytran2015, Determining local magnetic declination by a magnetic compass, survivaltricks.wordpress.com , Determining local magnetic declination by a magnetic compass, posted on March 31, 2016.

[4]. tonytran2015, Finding directions and time using the Sun and a divider, survivaltricks.wordpress.com , Finding directions and time using the Sun and a divider., posted on May 6, 2015.

[5]. tonytran2015, Finding North direction and time using the hidden Sun via the Moon, survivaltricks.wordpress.com, Finding North direction and time using the hidden Sun via the Moon . Posted on July 6, 2015.

[6]. tonytran2015, Finding North direction and time by stars, survivaltricks.wordpress.com, Finding North and time by stars. Posted on August 28, 2015

[7]. tonytran2015, Finding accurate directions using a watch, posted on May 19, 2015 .

DirectionBySun_12N

.

RELATED SURVIVAL blogs

Selecting and using magnetic compasses, posted on July 9, 2016

JapLensatic

,

Determining local magnetic declination by a magnetic compass, posted on March 31, 2016

Compass-Magnetic

, posted on June 14, 2016

compassflipMEDIUM

Shadow stick navigation and graph of solar paths, posted August 19, 2016


, posted on 2018 July 10

Find North By Fingers

Measuring angles and distances for outdoor survival, posted on June 29 2016 ,

DistPole

Finding North direction and time using the hidden Sun via the Moon . Posted on July 6, 2015This is a useful technique.

moonshapesnangles4c.jpg

Finding North direction and time using the Moon surface features. Posted on July 1, 2015. This is a useful technique.

wpid-wp-1435755781395.jpeg

, posted on

Circumpolar Stars Nth

Finding North direction and time using geological features, plants and animals, posted August 04, 2017

Indian mariners had first use of magnetic navigational compasses., posted August 24, 2018, Navigating with an AM MW radio receiver, posted January 17, 2017 The Scorpius constellation, posted January 8, 2017, The Orion constellation., posted December 26, 2016, Rice as emergency food., Using GPS in off-grid situations, Slide Sky-Disks with grid masks showing azimuths and altitudes, Slide Sky-Map for displaying tropical stars.

Click here for my other blogs on divider43.jpgSURVIVAL

divider43.jpg

polymeraust100dollars

Click here go to Divider63D400 Home Page (Navigation-Survival-How To-Money).

SUBSCRIPTION: [RSS – Posts], [RSS – Comments]

MENU: [Contents][Blog Image of Contents ][Archives ] [About]

Selecting and using magnetic compasses.

Selecting and using magnetic compasses

by tonytran2015 (Melbourne, Australia).

Click here for a full, up to date ORIGINAL ARTICLE and to help fighting the stealing of readers’ traffic.

#find North, #finding North, #compass, #select, #use, #operate, #North, #magnetic.

Selecting and using magnetic compasses.

A magnetic compass uses the local magnetic field generated by the rotating core of the earth to give the rotational axis of the earth. The two directions are reasonably close.

The magnetic compass is a secondary directional instrument to people who can observe celestial bodies for navigation but is a primary practical directional instrument to people who cannot observe any Celestial body. (Gyro-compasses are too expensive for most people).

Here is the list of desirable features for selecting a compass and different usage modes of magnetic compasses.

A compass should have at least the following desirable features:

1. Robustness,

2. Durability,

3. Wide operational conditions (being stable despite harsh operating conditions),

4. Accuracy (being true and sensitive),

5. Simplicity,

6. Portability, and

7. Versatility.

1. Robustness.

Magntic Compasse

Figure 1:(Left to right) Tiny liquid filled disc compass, simple compasses with and without needle lock.

Compass Meridional fake

Figure 2: A HAZARDOUS Chinese imitation of the German Kasper & Richter Meridian sighting compass, the imitation has its graduation markings self-detached after only washing by clean water from a tap! The black markings on the white rotating dial under the top circular glass can be seen lying randomly after peeling off.

A serious compass should be able to withstand falls of 2m into boxes of sands, to withstand hot and cold environmental temperatures, to withstand immersion in water, to withstand strong sunlight.

The liquid inside a liquid filled compass reduces stresses on the pivot caused by linear acceleration on the mass of the compass needle assembly; this makes the compass more robust. Serious dry compasses should have needle locks to remove acceleration stresses on pivots.

Liquid filled compasses should have pivots with spherical heads. These spherical heads need to be covered by lubrication fluid in operation but last longer than those with pointed conical head.

The Chinese, tiny (originally liquid filled) compass of Figure 1 has completely dried up after about one year of usage. However, it can still correctly point North when given gentle vertical vibration during use.

Figure 2 shows a hazardous Chinese imitation of the German Kasper & Richter Meridian sighting compass, the imitation has its graduation markings self-detached after only washing by clean water from a tap! The black markings on the white rotating dial under the top circular glass can be seen lying randomly after peeling off. (The blue line markings are mine to show what were there). This may lead to a SERIOUS situation to its inexperienced user while in the field. This type of products should be banned in Western countries.

2. Durability.

Compass Magnetic

Figure: An old ex-US Army lockable dry compass (made around 1965, initially known as M-1950 compass) from disposal stores remains robust and can keep on working although the clear glass has become partially clouded.

Any serious and expensive compass should withstand the passage of time (being durable).

Some types of PVC materials disintegrate with time. Some clear plastic may become cloudy with time. Some liquid filled compasses leak and dry up with time. The needle points of some dry compass may rust away with time.

3. Wide environmental tolerance in many modes.

Compass Lensatic Chinese

Figure: A Chinese lensatic compass with unreadable direction graduation due to wrong focal length of its lens. The round sighting lens has to be disassembled and reground and it is placed on the clear dial near to the 260 degree position of its rotating compass rose. ===>> All functioning parts of any compass must be tested before taking it to the field!

A compass should function even in non-level position or with highly inclined magnetic field, with unsteady hand holding, in cold or hot temperature, at normal or high altitude, when submerged in water, during the day or at night.

It should be able to function in its different operation modes.

Conical cup bearing on needles are more tilt tolerant. Low center of gravity of a needle allows the compass needle to resist the vertical tilt of any highly inclined magnetic field. Liquid filled compasses with non-flexible liquid capsules need to have allowance for non-interfering bubble or have undulating flexible bottom to allow volume change of the fluid. Temperature extremes and external atmospheric pressure can change the volume of the fluid and make liquid filled compasses leak. Any air bubble in its liquid capsule will reduce the till tolerance of a liquid damped compass. A capsule with air bubbles inside will cave in under external pressure and may crack when used for diving.

Mirror compasses also allow magnetic readings free from users’ own magnetic field.

Testing for tilt tolerance:

Tilt the compass in various directions until contact friction affects the reading. Work out the angle of tilt that still allow smooth operation of the needle. Work out the pitching of the needle due to the pitching of magnetic field. Check if this pitching can cause contact friction between the needle or compass rose plate and the case.

Night vision:
Night vision can be provided with either phosphorescent paint or radiation illumination. Phosphorescence requires energizing by a torch for few seconds every hour. Radiation is only acceptably safe if it is from Tritium.

4. Accuracy.

Compass Lensatic

Figure 1: Horizontal rotation test to detect resolution and cogging.

Compass Jap. Lensatic2

Figure 2: Japanese compass with agate jewel. The bearing on its rotating disc has an agate center, in contrast to the Chinese compass of Figure 1 with all metal bearing (no jewel).

Figure 3: Japanese compass with agate jewel. The bearing on its rotating disc has an agate center, in contrast to the Chinese compass of Figure 1 with all metal bearing (no jewel).

a. The compass should correctly show the magnetic North. (I have seen some cheap liquid damped compasses with the needles glued to the disks with enormous errors of about 20 degrees from their intended positions!)

b. The readings should then increase or decrease by values equal that caused by the horizontal rotation of the aiming line. This is required for interchangeability of data.

Accuracy test.

– Draw two pencil lines intersecting at right angle in the center on a piece of paper.

– Place the paper on a flat table face with one of the line accurately aligned along the magnetic field.

– Place the compass at the intersection at the center of the paper and read the direction of the needle relative to the pencil line.

– Smoothly rotate the compass case in one direction about the needle pivot to discover any cogging caused by any inappropriate use of magnetic material in the case. The induced eddy current in the non-magnetic material is too weak to cause any cogging. An accurate compass should not have any cogging.

– Smoothly rotate the compass case in the other direction about the needle pivot to discover any cogging caused by any inappropriate use of magnetic material in the case.

– Let one pointed magnetic pole of a long magnet comes gradually close to the compass along a spiraling path and check if one of two ends of the compass needle points exactly at it.

Without accuracy, your compass may send you astray by up to 20 degrees !

Accuracy test is a difficult one. It requires a uniform magnetic field with known orientation and strength. The magnetic needle of the compass should be symmetrically manufactured and magnetized. We must first eliminate compasses with obvious manufacturing defects on needle (being non-symmetric, badly mounted to the rotating needle disk). Accuracy requires:

1/- The dial must be circular and evenly graduated.

2/- The pivot of the needle must be exactly at the center of the circular dial and the pivot to be at right angle to the dial surface for the reading to be correct.

3- The magnetic needle must be metalurgically symmetric with respect to its center line.

With all different orientation of an accurate compass the two ends of the magnetic needle point to readings with difference of 180 degrees all the time. Even if a magnetic needle looks externally symmetric, its material properties may not be uniform. The metallurgical and mechanical history of a piece of material will definitely affect its magnetic properties. Only sprinkled iron powder can reveal the magnetic field of a compass needle. For this reason users have to stay away from cheap compasses with needles made from steel off-cuts and scrap materials as the needles may not be able to be magnetized to bear symmetric magnetic field.

If your compass is accurate it should give the accurate magnetic declination figure for your area from Sunrise and Sunset directions or from True North given by your street maps. The yearly figures for magnetic declination can be found from the internet for comparison.

Some quality compasses can provide accuracy of up to one degree. This gives accurate identification of destination and reduces unnecessary turnings. Accurate direction is vital when calling for base support.

Resolution test:

This test finds out how much change in direction can remain undetected by your compass.
1/- Find a level, steady surface, away from any magnetic source to place the compass .

2/- Set the compass sight on some easily seen object.

3/- Rotate compass anti-clockwise by about 90 degrees. Slowly and gently rotate the compass back into sighting position aiming at the same object. Write down the first reading for bearing.

4/- Rotate compass clockwise by about 90 degrees. Slowly and gently rotate the compass back into sighting position aiming at the same object. Write down the second reading for bearing.

5/- The two readings should differ by no more than 2 graduation units.

The difference is called the resolution of the instrument. A respectable instrument maker would not give a finer scale than the instrument can ever resolve! If the resolution is less than half a unit, the reading is meaningful to the last graduation unit.

The Japanese lensatic compass in figures 2 & 3 has jewel bearing at the center of the compass needle to reduce rotational friction. This is clearly shown in contrast to the cheap Chinese compass of figure 1.

5. Versatility.

Compass Mirror Hong Kong

Figure: Simple compass made of steel needle, clear plastic capsule, glass mirror and flexible case. This compass is not liquid damped, has no jewel bearing, and its mirror has no see through hole for aiming. It is NOT a serious compass !

Figure: A low cost 75mmL X 40mmW plastic mirror-compass with thermometer and relative hygrometer on its top cover. The inside of the top cover has a bright 75mm X 40mm metal mirror.

Extra features like mirror, lenses may help with grooming, fire making, observation, signaling.

Figure 3 of Step 1 shows a design with a bull eye for leveling and a vertical scale. Vertical graduation and accurate leveling of base allow determination of elevation.

The sighting mirror of the mirror compass in figures 1 and 2 of step 8 can also be used as a signaling mirror and personal mirror. This feature was favoured in the 1940’s.

Being waterproof and unsinkable
This is a requirement for adventurers, hikers and fishermen. If the compass is waterproof and light, it can float in water. A number of liquid filled compasses with plastic cases are light and can be made unsinkable if glued to some thick sheets of light styrene foam.

6. Simplicity.

Sighting Compass Imitation

Figure 1: A simple, plastic compass based on the Suunto compasses for touring. Please note that this imitation compass may be neither as durable nor as reliable as the genuine one.

 Sighting Compass Imitation 2

Figure 2: A simple, plastic compass based on the Suunto compasses for touring. Please note that this imitation compass may be neither as durable nor as reliable as the genuine one.

Sighting Compass Imitation

Figure 3: A simple, plastic compass based on the Suunto compasses for touring. Please note that this imitation compass may be neither as durable nor as reliable as the genuine one.

Figure 4: A high quality Suunto compasses for marine, professional and outdoor use (Image added after 2018 May 07).

A well made, simple compass rarely has malfunction and the first sign of any malfunction is obvious to see.

Liquid filled compasses will show bubbles when any liquid is lost and the malfunction and loss of robustness are gradual.

7. Portability.

A compass should be light and small enough to be carried around.

Robust but cumbersome or heavy compasses make users unnecessarily tired, I would not carry them. They are only good for laboratories or surveying teams.

If a compass has a holding ring or carrying string/strap, I would tie a string to that and pull the ring/string/strap with 10 times the weight of the compass to test its strength (10g acceleration endurance) before use, to prevent loss of the compass during field use.

8. Find North by a Compass: Magnetic and True Norths.

Magnetic Declination

Figure: True North, Magnetic North and Magnetic Deviation.

Obtain the magnetic deviation for your area. This deviation is commonly between (-45) degrees and +45 degrees and it slowly changes to a new value every year. The deviation is obtainable from the internet or by the method given in reference [2]. Positive magnetic declination means the Magnetic North is on the East of True North.

If you have a really erasable marker for your top glass/plastic dial, you can use it to mark the magnetic deviation from the long marking line for True North on your compass dial. The marking has to be erased and redone when the deviation has changed significantly. If you don’t want to mark on the dial, you can stick a tape on the underside of the compass and write clearly on it something like “MD = (-1)deg” (This is only an example value, your value is different).

Every time you use the compass, you only need to align the needle/rose to your marking on the dial and the long line for True North on your compass is already aligned.

If you do sighting using a compass with a rotating compass rose which always points to magnetic North, just read the graduation on the card and ADD the signed magnetic declination to it.

9. Precaution against magnetic anomalies.

Find North by watch

Figure: Cross checking directions with those from a Celestial method whenever possible is a desirable habit. This illustration is from reference [7].

Find North by the Sun and a divider

Figure: Cross checking directions with those from a Celestial method whenever possible is a desirable habit. This illustration is from reference [4].

Besides magnetic deviation caused by the core of the earth, there are also deviations near ground surface caused by man-made objects and ore bodies. These are called “Magnetic Anomalies”. An anomaly produces non-parallel magnetic field lines and non-constant magnetic field strength.

The following steps help to detect any magnetic non-uniformity in order to detect such anomalies and to avoid disorientation when using a magnetic compass (A magneto-meter is better for this detection as it supplies the extra accurate value of field strength but it requires batteries.).

1/- Count the yaw and pitch oscillation frequencies of the needle of any new compass. Write them on a piece of paper for future reference.

2/- Check the polarity and the yaw and pitch frequencies before packing the compass for any trip. If the frequencies have decreased the needle may have lost part of its magnetism and re-magnetization may be needed.

3/- Have a habit of cross checking directions with those from Celestial methods (given in references [4,5,6,7]) whenever the Sun or the Moon or bright stars can be seen. The cross checking with the direction determined by the method given in [7] also verifies that your watch is still working.

4/- Frequently take the bearing of your destination in both standing and crouching/sitting positions (with different heights), even if you are confident of your current position. This ensures that your compass is ready when needed and you are prepared against any sudden loss of visibility (due to change in weather, terrain, falling down a crevice! . . .). Any quick change in magnetic direction with height or with horizontal travel distance usually reveals a very strong, meter-scaled magnetic anomaly. The anomalies may be caused by buried metal objects (steel-reinforced bunkers, car bodies, tank bodies, unexploded bomb-shells!, magnetic ores,…) or even induced magnetic field from high voltage power lines.

5/- If anomaly is suspected, count the yawing frequency of the needle. The external field strength acting on the needle is proportional to the square of this frequency. For example, if the frequency goes up by 2, the external magnetic field strength may have gone up by 4.

6/- Distant objects such as mountain peaks, light houses, transmission towers can help detecting the sudden change in magnetic deviation when you travel. The magnetic bearings of these distant objects should only change slowly. If there is any sudden change in their bearings you may have to check the accuracy of your compass or the change in magnetic deviation.

Note:

Compasses are usually NOT suitable for rail travelers as the carriage bodies and the rails underneath it creates magnetic abnormality.

10. A special mode of operation to reduce own influence.

Compass mirror Chinese

Figure 1: Plan view of a plastic mirror compass. The mirror is opened by 110 degrees from its close position.

Compass mirror Hong Kong

Figure 2: End (operational) view of the same mirror compass. The mirror is opened by 45 degrees from its close position. The clear capsule should be rotated by the thumb until the fluorescent double II marking on it is on top of the North end of the needle. The compass should be hold in the air by the hand of a stretched arm.

Using the Mirror Sighting compasses.
The Mirror Sighting compasses are for a special mode of operation with reduced influence from user’s magnetic field. This feature allows the compass to be used with stretched arms keeping it away from the user’s body. A mirror compass is used in the following way:

Hold the mirror compass at your eye level, horizontally level on one stretched arm, away from your head, with the mirror tilted from the vertical by 45 degrees to let your eyes see the reflection of the working horizontal needle and dial of the compass. Take aim of the destination by the aiming guide and observe the horizontal magnetic needle through the mirror. Rotate the rotating dial on top of the needle to mark the position of the needle. For accuracy, keep the vertical marking line on the mirror superimposed on the aiming diameter of the horizontal dial of the compass. Finally bring the compass to your comfortable reading distance to read the marked position of the needle. The magnetic bearing of the aiming line is the value on the scale at the point nearest to the mirror.

This is a desirable feature if the user carries magnetic items and it is not practical for him to take off these items when using the compass. The sighting mirror can also be used as a signaling mirror and personal mirror. This feature was favoured in the 1940’s.

The compass in figure 2 has only a very crude aiming guide. It follows the design of Silva Trekker compasses.

Using the lockable compasses.

Compass M1950 away from body

Figure 3: Hand posture for holding type M-1950 compass for sighting with a stretched arm. The finger through the brass ring is the middle finger. The sighting is carried out using the slit in the sighting tab and the wire in the lid. The lens has no function in this sighting mode. This is my own novel mode of operation not designed by the makers of type M-1950 compasses.

Any tilt tolerant, lockable compass can also be used in this mode (with reduced accuracy) even without any mirror. Tilt tolerance ensures that the needle can point North before the lock is engaged to freeze it in place. The ex_US Army compass (model M-1950) in figure 1 of Step 2 can be used in this mode, and is surprisingly accurate, as it is tilt tolerant and the inertia of its rotating compass rose ensures that the needle orientation is retained while the lock is engaging. A lockable M-1950 compass is used in the following way (This is my own novel mode of operation, not designed by the makers of type M-1950 compasses. Do NOT complain to them that their compasses are not comfortable to use in this way!) :

Place the lid and the sighting tab of the M-1950 compass in vertical positions to have the compass in unlocked and operating condition. Turn the holding ring near the sighting tab fully downward. Curl the middle finger of your hand and stick it through the holding ring of the compass. Grip the compass by pressing the end of the index finger against the lid hinge and the joint of the thumb against the sighting hinge. Stretch your arm while holding the lensatic compass horizontally level at the height of our eyes, away from your head, with its lid vertical and its lock still fully disengaged (sighting tab in vertical position).

Take aim of the destination by the aiming guide then hold till for 3 seconds. Gently engage the lock (push the sighting tab into horizontal position) by only raising only the first joint of your thumb to push against the bend of the sighting tab while keeping the rest of the body motionless. After having been locked, the whole compass is bought to your comfortable reading distance to read the locked position of the needle. The magnetic bearing of the aiming line is the value on the compass rose at the point nearest to the hinge. It is hard to read but is definitely readable even with the sighting tab fully down.

11. Special Operating mode 2: Using small, fluid deficient compasses.

Compass Tiny 1

Figure 1: A two years old Chinese key-ring compass (with diameter of about 20mm) has visible air bubbles. Some bubbles or all bubbles may stick under the compass disc, under the S.

Compass Tiny 2

Figure 2: A two years old Chinese key-ring compass (with diameter of about 20mm) has visible air bubbles. Some bubbles or all bubbles may stick under the compass disc, under the SW.

Compass tiny 3

Figure 3: The compass is tilted by 100 degrees to have all bubbles collected at the upper side of the compass disc.

Compass Tiny 4

Figure 4: All gas/air is now above the compass disc.

A fluid deficient liquid filled compass should be repaired and refilled with the same type of fluid to restore its original, designed performance. However, a small such compass can still be used in reduced performance mode (for emergency) employing the following work around.

The capsule of of the liquid filled compass should be held upright. It is then tilted 100 degrees from its upright position to let any bubbles from underneath its compass rose (rotating disk) escape to the space at the top of the (now vertical) rim of the rose. The capsule is then tilted back to its upright position, ensuring that all air stays above the rotating rose. With all air expelled to the top of the compass rose, the latter can rotate although with reduction in accuracy because of undue tilting torque exerted by air bubbles.

Gentle tapping and vibration in the direction of the pivot axis will free the rose in multiple short time intervals while it travels/bounces between extreme positions. This is sufficient to make the magnetic needle of the rose point close to magnetic North.

Any small, completely dried, liquid filled compass may be made pointing North by such gentle vibration/rattling.

The method in this section may not be applicable to large marine compasses without Cardan gimbal mounts!

12. Special Operating mode 3: Using compasses balanced for the other hemisphere.

The magnetic field generated by the interior of the Earth looks like that of a giant dipole magnet placed at the center of the Earth and of length equal to the radius of the Earth. At the equator the field is parallel to ground surface while it goes into the ground away from the equator.

On the Northern hemisphere the North end of a compass needle is pulled towards the ground while on the Southern hemisphere the corresponding South end is.

This may make the ends of a symmetric compass needle in a thin circular compass touch the upper or lower part of the case, causing dragging friction.

The problem has two simple solutions for compass makers. Firstly the center of gravity of the needle should be made much lower than the tip of the pivot. Secondly, one needle end can be made heavier than the other to resist the pitching caused by the inclination of the magnetic field.

Most compass buyers live in Northern hemisphere so compass makers tend to make their products work from the equator to about 60 degrees Northern latitude. They just simply make the South ends of their compass needles heavier than the North ends. The so made compasses are said BALANCED for Northern hemisphere. You can notice that the North ends of their needles mostly rise up when used near the equator.

When these compasses are brought to the Southern hemisphere the South ends of their needles are pulled even further down, resulting in dragging.

A user on the Southern hemisphere may have to hold his compass case at angle to avoid dragging or to RE-BALANCE the needle by wrapping some copper wire around the Northern half of the compass needle.

Re-balancing requires delicate work on the compass and requires opening it every time you move to the other hemisphere. Here I offer a very effective and simple method of using the same compass in both hemispheres.

My solution is to magnetize the light end of the needle to be a North pole when in the Northern hemisphere and a South pole when in the Southern hemisphere. (The colour on the needle should now only mean a light or a heavy end.)

The method and the simple tools to re-magnetize a steel compass needle has been described in a previous Instructables posting, reference [1].

A compass with non-steel needle cannot be re-magnetized by this method.

Please leave any comments and suggestions here so that the posting can be improved !!

References.

[1]. tonytran2015, Beware of perilous flips by magnetic compasses, survivaltricks.wordpress.com, , posted on June 14, 2016.

[2]. tonytran2015, Determining local magnetic declination by a magnetic compass, survivaltricks.wordpress.com , Determining local magnetic declination by a magnetic compass, posted on March 31, 2016.

[4]. tonytran2015, Finding directions and time using the Sun and a divider, survivaltricks.wordpress.com , Finding directions and time using the Sun and a divider., posted on May 6, 2015.

[5]. tonytran2015, Finding North direction and time using the hidden Sun via the Moon, survivaltricks.wordpress.com, Finding North direction and time using the hidden Sun via the Moon . Posted on July 6, 2015.

[6]. tonytran2015, Finding North direction and time by stars, survivaltricks.wordpress.com, Finding North and time by stars. Posted on August 28, 2015

[7]. tonytran2015, Finding accurate directions using a watch, posted on May 19, 2015 .

DirectionBySun_12N

NorthByWatch2

Added after 2018 Feb 19:

[8]. “The compass was first used in India, around 1800 BC, for Navigational purposes and was known as “Matsya yantra” (which roughly translates to fish machine) because of the placement of a metallic fish in a cup of oil. The use of the magnetic compass started from 4th century in china, where a type of magnetite known as “lodestone” was used as a tool in a kind of divining magic, Geomancy. The Chinese were the first ones to have mastered the use of magnetic iron for navigation, which then rapidly spread to Europe and beyond.”, .https://knowledge4civil.wordpress.com/2017/07/23/types-and-uses-of-compass/

[9]. https://misfitsandheroes.wordpress.com/2018/01/15/fat-boys-magnetism-and-magic/

RELATED SURVIVAL blogs

Determining local magnetic declination by a magnetic compass, posted on March 31, 2016,

Finding North with a lensatic compass, posted on August 21, 2017

Compass-Magnetic

, posted on June 14, 2016

compass reversal

,

Shadow stick navigation and graph of solar paths, posted August 19, 2016

Measuring angles and distances for outdoor survival, posted on June 29 2016 ,

DistPole

Finding North direction and time using the hidden Sun via the Moon . Posted on July 6, 2015This is a useful technique.

moonshapesnangles4c.jpg

Finding North direction and time using the Moon surface features. Posted on July 1, 2015. This is a useful technique.

wpid-wp-1435755781395.jpeg

, posted on Circumpolar Stars Nth

Finding North direction and time using geological features, plants and animals, posted August 04, 2017

Navigating with an AM MW radio receiver, posted January 17, 2017 The Scorpius constellation, posted January 8, 2017, The Orion constellation., posted December 26, 2016, Rice as emergency food., Using GPS in off-grid situations, Slide Sky-Disks with grid masks showing azimuths and altitudes, Slide Sky-Map for displaying tropical stars.

Click here for my other blogs on divider43.jpgSURVIVAL

divider43.jpg

polymeraust100dollars

Click here go to Divider63D400 Home Page (Navigation-Survival-How To-Money).

SUBSCRIPTION: [RSS – Posts], [RSS – Comments]

MENU: [Contents][Blog Image of Contents ][Archives ] [About]

Beware of perilous flips by magnetic compasses

Beware of perilous flips by magnetic compasses

by tonytran2015 (Melbourne, Australia).

Click here for a full, up to date ORIGINAL ARTICLE and to help fighting the stealing of readers’ traffic.

#compass, #flip, #reversal, #compass reversal, #compass flip, #re-magnetize, #navigation, #survival, #find North, #finding North,

There has been warning by a Mountaineering expert that many people got into perilous situation when their compasses unexpectedly flipped direction prior to critical use. The Mountaineering Council of Scotland has issued warning on this danger.

This posting gives a method to re-magnetize and set at will the direction of any compass needle. The basic steps in guarding against unexpected flipping of magnetic compasses are also shown.

One possible cause of flips by magnetic compasses.

When a magnetic compass is stored its needle can not swing or cannot swing fast enough to follow the change in magnetic field.

If a strong magnetic field is forced through the needle from one end to the other, the needle will be magnetized by this strong field.

Therefore when your compass is stored in your bag and a strong magnet approaches it faster than the needle can rotate to adapt to change, the new field may be able to force a magnetic flux from one end of the needle to the other end and re-magnetize the needle. This occurrence is not rare.

Proof and applications.

compassflipMEDIUM

Figure: The reverse-magnetized needle of the compass with clear case

The first pictures shows that the needle of the clear based compass is pointing in the opposite direction to that given by the reference, metal cased compass. The needle has been magnetized into the flipped condition.

Re-magnetize the needle again

compassRestoredMEDIUM.jpg

Figure: The re-magnetized needle of the compass with clear case.

The compass needle was then successfully re-magnetized back into normal condition. It again points in the normal direction.

So I have been able to re-magnetize (in any direction of choice) the needle of a compass (the clear based compass with a mirror) as shown in the first two pictures. The magnet I used costs me under $0.30USD and is shown in the third, composite picture.

Re-magnetizing the needle of any compass

CompassToolsMEDIUM

Figure: Tools for Re-magnetizing the needle of any compass.

1/- To re-magnetize a compass, it is preferable to have a single pole P of a strong magnet far away from its other poles. Lay the compass up-side-down. Find out the end A of the needle that is repulsed by P. Push that pole P to the center of the needle, then move P towards that end A. When P has reached the end A and attracted that end, the needle has been re-magnetized.

It is even better if you can supply another single pole Q of opposite polarity to also touch the other end B of the needle. Otherwise, just use the compass just re-magnetized by the single pole P.

2/- The above re-magnetization shows that it is preferable to have long, observable needles for compasses.

3/- If you carry any strong magnets make sure that they are closed by closing irons to keep their magnetic lines within the vicinity of the magnets and the lines do not affect your compass.

The magnet I used is a fridge magnet of the rare earth type, it costs under $0.30 USD.

Avoidance and detection of flipping of a magnetic compass.

On acquisition of a compass, you should

1/- inspect it for any damage,

2/- count the swing, roll, and pitching vibration frequencies of its needle and make a written record,

3/- check the pitching of the needle and make a written record.

Before packing the compass for each field travel, you should

1/- inspect it for any damage,

2/- compare its swing, roll, and pitching vibrations of its needle with the written record made on acquisition,

3/- check the pitching of the needle and compare against the written record made on acquisition.

4/- have the polarities of the strong magnets on your phone case marked on a sketch (showing which magnets attract which ends of the needle). A copy of the sketch should be carried with the compass.

Before each field use, you should

1/- inspect your compass for any damage,

2/- carefully check the pitching of the needle (If a flip has occurred, the pitching also changes as the North pointing end usually balanced to point horizontal. If the North end pitches in any other way, the needle may have flipped.),

3/- slightly and slowly move the compass towards the phone case to see if the attraction pattern is still the same.

4/- If the vibration patterns are noticeably different the compass may have been damaged or may be in a stronger or weaker than normal (abnormal) magnetic field. You need to think about possible causes and effects.

5/- The above steps only help to detect any unexpected flipping, you still has to carry out all other procedures recommended by the maker of the compass.

Your compass usage should be more reliable with these extra precautionary steps.

Reference.

[1]. Heather Morning, Calling ALL Hill Walkers,The Mountaineering Council of Scotland, http://www.mcofs.org.uk/navigation-reversed-polarity.asp, posted on April 2013.

Related SURVIVAL blogs:

Determining local magnetic declination by a magnetic compass, posted on March 31, 2016

Compass-Magnetic

Selecting and using magnetic compasses, posted on July 9, 2016

JapLensatic

Click here for my other blogs.

divider43.jpg

polymeraust100dollars

Click here go to Divider63D400 Home Page (Navigation-Survival-How To-Money).

SUBSCRIPTION: [RSS – Posts], [RSS – Comments]

MENU: [Contents][Blog Image of Contents ][Archives ] [About]

Determining local magnetic declination by a magnetic compass

Determining local magnetic declination by a magnetic compass

by tonytran2015 (Melbourne, Australia).

Click here for a full, up to date ORIGINAL ARTICLE and to help fighting the stealing of readers’ traffic.

#compass, #magnetic compass, #determine, #find North, #finding North, #magnetic declination, #Magnetic North, #sunrise, #sunset, #True North

A magnetic compass can be used to determine local magnetic declination. This declination varies with location and time.

Magnetic Declination

Figure: True North, Magnetic North and Magnetic Deviation.

The declination is compiled from local laboratories data and made into world charts for navigation but each person can also determine his current local declination by himself.

Step 1: Requirements

Compass Magnetic

Figure: Magnetic compass, dry, eddy-current-damped, ex-US Army.

We require:

1. A place where both Sunrise and Sunset can be observed,

2. Parallel magnetic field lines for the whole place, that is the direction of the magnetic needle does not change when the compass is moved around in such a place, and

3. A sighting compass as in the picture.

Step 2: Determining local magnetic declination.

Keep the sighting compass level and read the direction of Sunrise.

Keep the sighting compass level and read the direction of Sunset.

The bisector line of the two readings is the true North. The reading for the bisector is the mean value of Sunrise and Sunset values.

The reading of the bisector line is the absolute value of magnetic declination. Magnetic declination is positive when magnetic North is East of true North and negative when West.

RELATED SURVIVAL blogs

Finding North with a lensatic compass, posted on August 21, 2017

Compass-Magnetic

, posted on June 14, 2016

compassflipMEDIUM

Selecting and using magnetic compasses, posted on July 9, 2016

JapLensatic

Navigating with an AM MW radio receiver, posted January 17, 2017, The Scorpius constellation, posted January 8, 2017, The Orion constellation., posted December 26, 2016, Rice as emergency food., Using GPS in off-grid situations, Slide Sky-Disks with grid masks showing azimuths and altitudes, Slide Sky-Map for displaying tropical stars.

Click here for my other blogs on divider43.jpgSURVIVAL

Click here go to Divider63D400 Home Page (Navigation-Survival-How To-Money).

SUBSCRIPTION: [RSS – Posts], [RSS – Comments]

MENU: [Contents][Blog Image of Contents ][Archives ] [About]

Finding North direction and time using the hidden Sun via the Moon

Finding North direction and time using the hidden Sun via the Moon.

by tonytran2015 (Melbourne, Australia).

Click here for a full, up to date ORIGINAL ARTICLE and to help fighting the stealing of readers’ traffic.

(Blog No.006).

#find North, #finding North, #compass, #direction, #time, #Sun, #hidden Sun, #navigation, #survival, #Moon, #phase,

Finding North direction from the Moon cannot not be as accurate as from the Sun. There are many causes for this:
1/- The Moon does not always rise on the principal East (at 90 degree of the compass rose).
2/- We cannot work out by heart the Moon’s declination (up to +/- 5.1 degrees to the ecliptic, and 23.5+5.1 degrees to the Celestial equator ).
3/- We cannot easily work out when the Moon reaches its highest elevation angle at its meridian time. The Moon does not often cast strong shadows for shadow sticks to work.
Here I describe my new method to find out North direction and time with improved accuracy. The method uses shape and position of the Moon, solar declination and user latitude to work out the position of the hidden Sun, then work out North direction and approximate local time with an accuracy of 30 minutes. Literally, the user can work out North direction and the local time with his bare hands.
I have field tested this method and I have relied on it for many years.

1. Basic information on the Moon for navigation.

image

image

Figure 1: Moon phase chart. Figure 2: A crescent Moon may not align itself to the terrestrial East or West horizon points (see texts).

The Moon is a satellite of the earth. Everyday Moon-rise and Moon-set time is retarded by about 50 minutes. This allows the Sun to travel further on its journey every subsequent night. Therefore after full moon the partial bright side stays on the East (trailing) side and dark crescent appears on the West and dark area gets fatter daily until the whole moon is dark. Similarly, from new Moon a bright crescent appears on the West and grows fatter and bright area gets fatter daily until full Moon is reached. However the bright and dark sides of a partial Moon rarely point accurately to East or West directions.

Figure 2 of this section shows a crescent Moon on the Celestial sphere. The horizontal great circle represents the horizon of the observer. The inclined great circle represent the Celestial equator and the arrow through the center of the sphere represents the Celestial axis. The circle parallel to the Celestial equator is a constant declination circle being the trajectory of the Moon during the hours. The two intersection points of the two great circles are the terrestrial East and West points of the horizon. This picture shows that the crescent Moon may point its bright to dark line far away from the terrestrial East or West points when there is a combination of high declinations of both the Moon and the Sun on the same side of the Celestial equator.

Each Lunar (Moon) cycle begins with the Moon being visible as a thin bright arc in the sky (called a New Moon), trailing the Sun by less than one hour. After Sunset this thin Moon is seen bright on the West until it sets. On subsequent days, the Moon is more and more behind the Sun, its position shifts gradually towards the East and the Moon remains for longer and longer duration in the night sky till full Moon day. After full Moon day, the Moon (now called a Late Moon) becomes thinner and thinner and is seen risen in the East in the night, it remains visible in the sky after Sunrise, and travels ahead of the Sun. On subsequent days, its lead on the Sun gradually reduces. Near the end of the cycle, the Moon is visible as only a thin bright arc rising in the East for less than one hour before Sunrise and after Sunrise it can still be seen leading the Sun by that same amount of time. At the end of the Lunar cycle, the Moon sends no reflection of Sunlight to Earth and is too close to the Sun to be visible in the day sky.

Keeping diaries of past days of full and new Moon helps people know where their time is in the current cycle, and so they know whether the leading (West) side of the Moon should be bright (new to full Moon) or dark (full to new Moon). Fortunately, the users of my method described here do not have to refer to any such records of the Moon.

It is interesting to note that Buddhist East Asians use lunar calendars and observe fasting at new and full Moon. From their calendar and their fasting festivals , they already know whether the Moon is waxing or waning. This may help explaining why they are good at finding North direction using the Moon.

CAUTION 1: The bright to dark line of the partial Moon can point far away from the terrestrial principal East or West directions.

CAUTION 2: The horn line of the partial Moon can point far away from the terrestrial principal North or South directions.

2. Moon shapes giving Moon-Earth-Sun alignment.

The various shapes of the Moon under various angles of lighting by the Sun are given in the illustration picture. The Moon goes through this cycle every 29.5 days. The picture is drawn for the principal values of the angle of Moon-Earth-Sun. The picture allows determination of the direction of the Sun from the shape of the Moon.
The angle Moon-Earth-Sun will be more accurately known if the navigator is in the habit of directly measuring and recording it before Sunset (few hours earlier) whenever the Moon is seen during day light.

3: Direction of the Sun from the Moon

image

image

The line joining the two horns of the Moon is always at right angle to the plane of Sun, Earth and the Moon. Draw a half-line from you to the Moon and extending far past the Moon. Imagine the Sun is at the far end of this half-line. Swing this half-line in the direction of the bright side (at right angle to the line joining the two horns) of the Moon to have the angle of Moon, Earth and Sun giving a matching shape for the brightened part of the Moon. The half-line then gives the direction of the Sun.
Alternatively, you can think of placing a sphere between you and the Moon, and a torch is is used to shine on the sphere and the torch is placed in various directions until it gives a partially brightened sphere similar to the current Moon shape.

4. Finding North direction and time.

image

image

image

image

image

image

divider43.jpg

With the direction of the Sun known, the technique given by my previous blogpost “Finding North direction and time using the Sun and a divider” [1] can be applied to find North direction and local time.
The selection rule of right or left hand placement of CA in “Finding North direction and time ising the Sun and a divider” has been generalized.

The generalization is:
(Northern latitudes with rising Sun or Southern lat. with setting Sun) ==> CA on the left of CB,
(Northern latitudes with setting Sun or Southern lat. with rising Sun) ==> CA on the right of CB.
The time for rising Sun here is from 0hr to 12hr (AM) and time for setting Sun here is from 12hr to 24hr (PM).
The rest of that method applies to the hidden Sun to give North direction as well as time.

I have tested and found that this method gives direction accurately and easily. The additional benefit is that it also gives approximate time.

Reference
[1]. tonytran2015, Finding North direction and time using the Sun and a divider, http://www.survivaltricks.wordpress.com/, 06 May 2015.

RELEVANT SURVIVAL blogs

Navigating with an AM MW radio receiver, posted January 17, 2017, The Scorpius constellation, posted January 8, 2017, The Orion constellation., posted December 26, 2016, Rice as emergency food., Using GPS in off-grid situations, Slide Sky-Disks with grid masks showing azimuths and altitudes, Slide Sky-Map for displaying tropical stars.
, posted on 2018 July 10

Find North By Fingers

Finding North direction and time accurately from the horn line of the Moon. posted on August 12, 2015. This is my novel technique.

image

Finding North direction and time using the Moon surface features. Posted on July 1, 2015.

image

, posted on

Click here for my other blogs on divider43.jpgSURVIVAL

divider43.jpg

polymeraust100dollars

Click here go to Divider63D400 Home Page (Navigation-Survival-How To-Money).

SUBSCRIPTION: [RSS – Posts], [RSS – Comments]

MENU: [Contents][Blog Image of Contents ][Archives ] [About]

Finding North direction and time using the Moon surface features

Finding North direction and time using the Moon surface features.

by tonytran2015 (Melbourne, Australia).

Click here for a full, up to date ORIGINAL ARTICLE and to help fighting the stealing of readers’ traffic.

#find North, #finding North, #compass, #direction, #time, #Moon, #surface features, #natural compass rose, #navigation, #survival

This article shows how to use the Moon for finding direction and time.
The surface features of the Moon can be used as a compass rose for Earth inhabitants.

1. An upside down natural compass rose

Near to full Moon the phase (waxing-waning) and horn-line methods are not accurate. Right at full moon they are not applicable. However at those times we may obtain directional information from the global map of the Moon using the colour and shade of its surface (soil) features. Since moonlight is only reflected light from the Sun and is not intense and we may look at the Moon’s surface for the features.

We have to identify the features of the Moon associated with Lunar own rotational poles, so that the Moon can be placed and aligned on an upside down compass rose aligned for the rotation of the Earth.

Each of us may have have different individual visualization (or a simplified picture) of the Moon to orientate its poles on such compass rose. My own visualization for the shades on the Moon is a small lion licking the face of a kneeling monkey and it is drawn on the Moon in the title figure.

image

Figure: The surface features of the Moon is used as the core of a compass rose.

2. An oscillating core of the compass rose !

image

Figure 1: Moon as an oscillating core of a compass rose.

image

Figure 2: Moon as an oscillating core of a compass rose.

image

Figure 3: Moon as an oscillating core of a compass rose.

Consider that compass rose an UNDERNEATH view of a normal compass rose and you can use it for finding directions when it is high in the sky. (The leading side of the Moon, with a lion visualization, is on our West and its trailing side, with a monkey visualization, East). However the North of the Moon is the North pole of Lunar rotation axis and it makes an angle with the axis of the Earth, the angle sometimes reaches 23.5 + 1.5 = 25 degrees. Imagine that you can walk on the Celestial equatorial plane and the Lunar axis is planted on it at an angle of 90-25 degrees and you go around it once every 27.3 days.

Looking at that inclined Lunar axis, you will see that axis alternately tilted to your right hand then to your left hand. Looking from the earth, the axis of the Moon appears to oscillate clockwise and anti-clockwise (with amplitude equal to the lunar orbit angle, which requires complex calculations, and can be up to up to 25 degrees ) as the Moon orbits around the Earth. This compass rose only gives correct orientation when the Moon is made oscillating inside it ! The North of the Moon is aligned to 0 degree only when the Moon goes through its maximum or minimum value of Lunar declination (at furthest distance to the Celestial equator). When the Moon crosses the Celestial equator, the angle between Moon axis and Celestial axis is highest in absolute value..

So we have a natural compass rose but we must remember that Moonscape features does not easily give accurate direction and the Moon oscillate inside our Earth aligned compass rose between up to +25 and -25 degrees as well as tilling its poles toward or away from us. The title figure of this article is made for the reference, mean orientation of the Moon, when its axis is at right angle to the line of view and its equator is aligned to 90-270 degree marks of the graduation ring. Users intending to use the compass rose on any full Moon should check the orientation of the surface features against the East West directions (given by Waxing-Waning rule and by adjusted horn line method) two or three nights prior to the full Moon. Otherwise an uncertainty of up to 25 degrees should be allowed with this compass rose.

3. Lunar navigation needs a combination of methods.

MoonShapesNAngles5C

Figure 1: Moon phase chart for a Solar declination of (-20) deg (South).

tiltedhornlinec2.jpg

Figure 2: Panoramic view of the travel of the Moon.

MoonRosePath
Figure 3: Panoramic view of the travel of the Moon.

Navigating by the Moon becomes easier when we do it nightly on consecutive nights and keep records from previous nights. At half-Moon times we can use the Waxing-Waning rule and my improved horn-line method (given in p2) to draw the Celestial axis line on the Moon then record the position of the horn-line on the featured surface. At full Moon times we use Lunar surface features with the angle for the Moon obtained previously from the 3/4 Moon nights.We have to remember that the horn-line rotates almost steadily about each full-Moon.

Alternatively, the if we form the habit (when we have to navigate) of daily recording the direct measurements of Lunar declination, from the Moon and the Celestial pole (by either stars at night or the Sun before Sunset), we have accurate values of Lunar declination. The Moon and its declination can then replace the Sun in my method of determining direction and time (reference [3]). The accuracy is further improved if we combine the knowledge of our latitude, the phase and elevation angle of the Moon to predict its trajectory for the night (therefore we already have had an initial estimation of the North-South direction).

After the North-South direction has been found it is easy to tell time from a full Moon as the Moon is trailing the Sun by about 12 hours.The estimation is more accurate if we apply extrapolation to our own records of Moon rises and Moon sets on previous nights. When there is no Moon, we have to use stars and that will open new topics.

With lots of switchings among methods, the navigators may find that finding direction and time via the hidden Sun as given in reference [1] the simplest.

References

[1]. tonytran2015, Finding North direction and time using the hidden Sun via the Moon,https://survivaltricks.wordpress.com/2015/07/06/finding-north-direction-and-time-using-the-hidden-sun-via-the-moon/, posted on July 6, 2015

[2]. tonytran2015, Finding North direction and time accurately from the horn line of the Moon. https://survivaltricks.wordpress.com/category/moon-horn-line/
posted on August 12, 2015

[3]. tonytran2015, Finding North direction and time using the Sun and a divider, http://www.survivaltricks.wordpress.com/, 06 May 2015.

RELATED SURVIVAL blogs
, posted on 2018 July 10

Find North By Fingers

Finding directions and time using the Sun and a divider., posted on May 6, 2015. This is my novel technique

wpid-dividermwp3e2c2.jpg

Finding North direction and time using the hidden Sun via the Moon . Posted on July 6, 2015

moonshapesnangles4c.jpg

Finding North direction and time accurately from the horn line of the Moon. Posted on August 12, 2015. This is my novel technique.

wpid-wp-1439376905855.jpeg

Finding North and time by stars. Posted on August 28, 2015

PolrNorthNC20const8

Finding North and time with unclear sky. Posted on October 17, 2015.

wpid-bstarsn20b.jpg

Navigating with an AM MW radio receiver, posted January 17, 2017, The Scorpius constellation, posted January 8, 2017, The Orion constellation., posted December 26, 2016, Rice as emergency food., Using GPS in off-grid situations, Slide Sky-Disks with grid masks showing azimuths and altitudes, Slide Sky-Map for displaying tropical stars.

Click here for my other blogs on divider43.jpgSURVIVAL

Click here go to Divider63D400 Home Page (Navigation-Survival-How To-Money).

SUBSCRIPTION: [RSS – Posts], [RSS – Comments]

MENU: [Contents][Blog Image of Contents ][Archives ] [About]

Finding accurate directions using a watch

Method for finding accurate directions by a common analogue watch.

by tonytran2015 (Melbourne, Australia).

Click here for a full, up to date ORIGINAL ARTICLE and to help fighting the stealing of readers’ trafficby tonytran2015 (Melbourne, Australia).

#find North, #finding North, #compass, #direction, #by Sun, #bisector, #using watch, #with watch, #tilted watch, #inclined watch, #navigation, #without compass

This method uses a common 12-hour watch with analogue face for finding directions. Unlike the traditional method of using the hour hand of a flat lying watch, my method uses a watch tilted from the vertical and gives better accuracy for both North and South hemispheres including tropical zones. When applied to the arctic and antarctic regions, the watch is tilted by more than 67 degrees and lies almost flat on the ground; it becomes the traditional method using flat lying watch.
This method use the position of the Sun, time and known latitude angle to determine directions and Sun declination (therefore estimation of current month of the year).
The method for Northern latitudes is described below.

Method for Northern latitudes.
The word “bisector” here is used to mean the bisector of the angle between the midnight/midday marking and the hour hand.

DirectionBySun_12N

The red line is the bisector. The line CB is drawn on a card representing the half-plane to enable accurate alignment to the Sun

WatchCompass_22NL

The bisector is in the opposite direction of a corresponding 24 hr hand on a 24 hr dial

1/- Hold the watch so that its AXIS rises above the horizontal plane by an angle equal to the latitude of the region. That is its face points to somewhere in the sky and its back is angled downwards into the ground.
2N/- Determine the half-plane limited by the axis of the watch and containing the bisector. This half plane revolves clockwise about the axis of the watch once every 24 hour and goes through the mid-day marking at noon.
3N/- Hold the watch in such composure and rotate your whole body around your vertical axis by your feet until the Sun lies in the above half-plane.
4N/- Alternative to step 3N, observer can determine on the semi-plane a half-line CB from the centre C of the watch dial, forming with the watch axis an angle equal to the angle between the direction to the Sun and the Celestial axis. The half-line CB starts from the center of the dial and is nearly in the direction of the bisector. It rises above the dial toward the glass and points through the glass of the watch during summer time and dives below the dial into the movement compartment of the watch and points through the movement of the watch during winter time. This half-line always points to the Sun if this watch displays the local time and the face of the watch and its axis point to the North Star. Instead of trying to have the half-plane containing the Sun, observer can try to have CB pointing to the Sun. This gives better accuracy.
5N/- At that position, the watch face and its AXIS are POINTING to the North Star. Tilt the watch further, until it lies horizontally. In this horizontal position, the mid-day marking is pointing South and the 6 o’clock marking is pointing North.

watchcompassJ

Figure: Summary of finding North by a watch. Red hand is the bisector of 0 hr direction and the hour hand; green hand is its reflection across the (6-12) axis. Axis C-BN for Northern hemisphere is parallel to red hand at equinox days and is (raised above)/(dipped below) the watch dial by 23 degrees at local summer/winter solstice. Axis C-BS for Southern hemisphere is parallel to green hand at equinox days and is (raised above)/(dipped below) the watch dial by 23 degrees at local summer/winter solstice. Green drawing marks are for Southern hemisphere and are the mirror reflection of red drawing marks.

Method for Southern latitudes.
The word “left-right flip of bisector” here is used to mean the the bisector the bisector of the angle between the midnight/midday marking and the hour after being flipped left-to-right, that is after being reflected across the line mid-day to 6 o’clock on the dial.

1/- Hold the watch so that its AXIS rises above the horizontal plane by an angle equal to the latitude of the region. That is its face points to somewhere in the sky and its back is angled downwards into the ground.
2S/- Determine the half-plane limited by the axis of the watch and containing the left-right flip of bisector . This half plane revolves anti-clockwise about the axis of the watch once every 24 hour and goes through the mid-day marking at noon.
3S/- Hold the watch in such composure and rotate your whole body around your vertical axis by your feet until the Sun lies in the above half-plane.
4S/- Alternative to step 3S, observer can determine on the semi-plane a half-line CB from the centre C of the watch dial, forming with the watch axis an angle equal to the angle between the direction to the Sun and the Celestial axis. The half-line CB starts from the center of the dial and is nearly in the direction of the bisector. It rises above the dial toward the glass and points through the glass of the watch during summer time and dives below the dial into the movement compartment of the watch and points through the movement of the watch during winter time. This half-line always points to the Sun if this watch displays the local time and the face of the watch and its axis point to the Southern Celestial pole. Instead of trying to have the half-plane containing the Sun, observer can try to have CB pointing to the Sun. This gives better accuracy.
5S/- At that position, the watch face and its AXIS are POINTING to the Southern Celestial pole. Tilt the watch further, until it lies horizontally. In this horizontal position, the mid-day marking is pointing North and the 6 o’clock marking is pointing South.

No ambiguity in equatorial latitudes.
The watch is placed almost vertically in equatorial latitudes by both methods. Methods for both Northern and Southern latitudes gives exactly the same outcomes.

Extension application for both hemispheres.

6/ This method applies equally well to the Moon when its declination as well as lateness relative to the Sun is known. If the Moon can be seen in day light, a navigator should continue from the so determined direction of the Celestial axis to take the declination of the Moon as well as its lateness (and its angular distance, which can be accurately measured using the divider) relative to the Sun for that day. He can then continue his accurate determination of Celestial axis during the Moon lit part of that night by replacing the unseen Sun by the Moon together with its value of declination and its lateness supplied by himself. (Remember that the Moon increases its lateness relative to the Sun by a further 50 minutes in every 24 hours).

Figure: Summary of finding North by a watch.

Actual field test.
The author has tested these methods and found them to be applicable, easy and accurate to much better than 30 degrees for latitudes from 0 to 40 degrees. The accuracy is better than 10 degrees when the Sun has low altitude.

Explanation notes.
N1/- The word “watch” here applies to any watch or clock.
N2/- When a watch or a clock dial is hung on a vertical wall, its midnight marking is at the highest position. If the hour hand of a watch completes one revolution in 24 hours the watch is called a 24-hour watch; if it completes in 12 hour the watch is called a 12-hour watch. Most watches and domestic clocks are 12-hour ones. The bisector of the midnight marking and the hour hand of any 12-hour watch complete one revolution in 24 hour. It moves like an imaginary 24-hour hand on that watch.
N3/-The axis of the watch is the oriented line (Note that it is more than “the oriented half-line”.) going through the center of the watch at right angle to its dial disc and is parallel to the rotation axes of both the minute pointer (or “minute hand”) and the hour pointer (or “hour hand”). The direction chosen on the line is from the back to the front face of the watch.
N4/- A watch display local time when it shows 12 o’clock when the Sun reaches its highest point in the sky.
N5/- The angle between the North Star and the Sun varies like a sine wave with amplitude of 23.5 degrees; it should be 90 degree during Spring and Autumn equinoxes and 90-23.5 degree at Northern Summer solstice (21st June) and 90+23.5 degree at Northern Winter solstice (21st of December).
N6/- To tilt the watch accurately as required by step1, we can carry out the following steps:
1a/- Note that hour markings on 12hr watch dials are separated by 30 degrees. Other angles can be similarly worked out.
1b/- Hold the watch verticaly with 0hr at highest position.
1c/- Rotate the watch (either left or right, it does not matter) by angle lamda, keeping its dial plane unchanged. The line 0hr-6hr now makes an angle lamda with the vertical line.
1d/- Keep the axis 0hr-6hr fix in space, rotate the watch around it until the dial is pointing upwards evenly. The watch dial is now tilted upward by the angle lamda.

Relevant to this topic is also a method of finding North and time using neither watch nor compass [1].

Reference

[1]. tonytran2015, Finding North direction and time using the Sun and a divider, https://survivaltricks.wordpress.com/2015/05/06/finding-directions-and-time-using-the-sun-and-a-dividing-compass/
posted on May 06th, 2015.

RELATED SURVIVAL BLOGS (Added in December 2016)

Caution in finding North by bisector line of a horizontal watch. Posted on October 28, 2015
, posted on 2018 July 10

Find North By Fingers

Finding directions and time using the Sun and a divider., posted on May 6, 2015. <<<—This is my MOST USEFUL novel technique.

wpid-dividermwp3e2c2.jpg

find North by the Sun

Finding North direction and time using the hidden Sun via the Moon . Posted on July 6, 2015

image

Finding North direction and time accurately from the horn line of the Moon. Posted on August 12, 2015. This is my novel technique.

image

Finding North direction and time using the Moon surface features. Posted on July 1, 2015.

image

, posted on

Finding North and time by stars. Posted on August 28, 2015

Sky map Northern 3/4 sphere

Sky map Southern 3/4 sphere

Finding North and time with unclear sky. Posted on October 17, 2015.

image

image

, posted July 22, 2016

DirectionTimeByStars

Click here for my other blogs on divider43.jpgSURVIVAL

divider43.jpg

polymeraust100dollars

Click here go to Divider63D400 Home Page (Navigation-Survival-How To-Money).

SUBSCRIPTION: [RSS – Posts], [RSS – Comments]

MENU: [Contents][Blog Image of Contents ][Archives ] [About]