Adding Longitude and Latitude Lines to a map

Adding Longitude and Latitude Lines to a map

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.78).

#find North, #GPS, #navigation, #off grid, #adding, #longitude, #latitude, #coordinate, #lines, #map,

Adding Longitude and Latitude Lines to a map.

Locating where you are using the internet is great but there are times when you have no mean to connect to the internet and you have to use GPS for positioning without any assistance via the internet. Such a situation may arise when you have no internet coverage or when going hiking.

If you want to use your GPS off-grid with any map, you need to draw on top of the map an accurate system of regularly spaced longitude and latitude coordinate lines.

This posting shows how to add the lines.

1. Making a map graduated with Longitude and Latitude Lines.

1. Choose a map with your required resolution and range. The resolution differs for different application: For city street maps resolution should be better than 2m, for country town maps, resolurion only need to be better than 5m as houses are widely separated, for touring, exploring maps, resolution can be upto the (1/10) of the visual range, etc…

2. Make sure that the top of the map points to true North. (In some countries, maps are deliberately oriented at angle to true North, probably for security reasons.)

Figure: Openstreetmap for Melbourne with 3 airport landmarks. Map is used under Open License from Open Street Map, the data are owned by Open Street Map Contributors.

3. On that map, find some unmistakable features such as a well known Airport or Helipad, a Light House, a TV Transmission Tower, a Town Hall, Churches, Schools, Cottages in a forrest, sharply defined mountain peaks, trail intersections… with known longitudes and latitudes. Their coordinates are usually given on the Internet or or easily extracted from Google Map or Navigating Apps.
Find two to four such fearures located near the four extreme corners of your map. They will be used as land marks.

Ecample:

The 3 landmarks that can be used here are:

a. Melbourne Tullamarine airport, Elevation AMSL 434 ft / 132 m, Coordinates 37°40′24″S 144°50′36″E

b. Melbourne Moorabin airport, Elevation AMSL 50 ft / 15 m, Coordinates 37°58′33″S 145°06′08″E

c. Melbourne Essendon airport, Elevation AMSL 282 ft / 86 m, Coordinates 37°43′41″S 144°54′07″E

4. On a separate fresh sheet of paper make a coordinate grid of longitude and latitude covering your range.
On this sheet with grid but no map, mark the coordinates of your land marks.

Figure: Melbourne Tullamarine and Moorabin airports on a grid map.

5. Check that the shape of the figures formed by the land marks are similar in both the grid sheet and the map. You may have to stretch or shrink the grid vertically and then horizontally to have a fit. The figures should be similar if no mistakes have been made. If the shapes are similar you can proceed to the next step.

6a, If the map and grid are both digital, they can be superimposed in the computer to produce the following map with added coordinate lines:

Figure: Openstreetmap for Melbourne with added cooodinates. Map has been modified from original map used under Open License from Open Street Map, the data are owned by Open Street Map Contributors.

The added lines are on round figure coordinates and are 2 minutes of arc apart. The intersection nearest to the NW of Tullamarine airport has coordinate (144°50′E, 37°40′S ).

6b. If you are using printed map: Join two distant landmarks on the coordinate sheet and notice where the lines of “minute of longititude” and of “minute of latitude” intersect it

7. If you are using printed map: Reproduce that line, with all its intersecting points, on the actual paper map.

8. If you are using printed map: From these intersecting points project corresponding vertical lines to make the “minute of longititude” lines and horizontal lines to make “minute of latitude” lines.

9. The map is now graduated with longitude and laritude lines.

10. Its grid can now be used as a base to draw finer grids for detail maps with higher resolutions.

2. Using GPS with maps.

You can download a (preferably topological) map of your area to practice drawing the coordinate lines, the constant altitude lines and learn about the accuracy of the values of longitude, latitude and altitude given by your GPS apps.

It is preferable to use topographic maps with old fashioned land marks (such as churches, tall towers …). Topographic maps give the additional constant ground altitude contours (relative to some mean sea level surface). Constant altitude curves are the faint brown curves on the map illustrated here. The height of each contour is given by a small number. The altitude values of 20m and 10m have been highlighted in this example map by two red circles.

Figure: Opentopomap for the area in my test. Map is used under Open License from Open Street Map, the data are owned by Open Street Map Contributors.

References

[1]. tonytran2015, Using GPS in off-grid situations., posted December 6, 2016

[2]. tonytran2015, Measuring angles and distances for outdoor survival, survivaltricks.wordpress.com,

https://survivaltricks.wordpress.com/2016/06/29/measuring-angles-and-distances-for-outdoor-survival/, posted 29/6/2016.

[3]. tonytran2015, Selecting and using magnetic compasses, survivaltricks.wordpress.com,

https://survivaltricks.wordpress.com/2016/07/09/selecting-and-using-magnetic-compasses/, posted 09/7/2016.

[4]. , BBC News, UK radio disturbance caused by satellite network bug, http://www.bbc.com/news/technology-35463347, 2 February 2016.

Added after 2018 Nov 26:

The Thors’ son urged people travelling to remote locations without mobile coverage to download a GPS application to their phones ahead of their journey, as well as an offline map for their destination.

[5]. https://mobile.abc.net.au/news/2018-11-26/german-tourists-died-central-australia-walked-17km-heat-stress/10554408

PREVIOUS SURVIVAL blogs

, posted on

Circumpolar Stars Nth

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

Compass-Magnetic

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]

Interesting maps of old Saigon

Interesting maps of old Saigon

by tonytran2015 (Melbourne, Australia).

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

1.Introduction

When old maps are laid over current satellite based ones, we have interesting maps giving insight into the evolution of land use, the technology and defense concepts in ancient time, etc.

Here are two maps, over 150 years old, placed over the current satellite based Open Street Maps, giving insight into the land use, technology, defense concepts in the 1800’s in South of Vietnam.

2. Map of the first Gia-Dinh (Saigon) Citadel (1790-1836) for the Vietnamese King.

This citadel was built by Colonel (mercenary?) Victor Oliver in 1790 for the first Nguyen king (a warring party).

SaigonThanhQuy

Figure: Overlay of an old map drawn in 1799 on current Open Street Map.

Original 1799 map has expired copyright. Open Street Map data are used under Open License. Open Street Map data are owned by Open Street Map Contributors (see website www.openstreetmap.org).

This old citadel was built to be a capital citadel with a residence for the King and his royal family. It appears like it has been designed against attack from North West. It had fewer firing towers on the South East side. It may be speculated that the Vietnamese King had had control of the sea and therefore the Saigon river (called Binh-Duong river at that time) on its South East.

To the North-West was the Khmer empire and the citadel was built to resist attacks from North West. It has a fighting wall, call Luy-Ban-Bich, extending out to its West.

The red line in the map denotes part of “Ban-Bich-Co-Luy”, semi-circular wall for fighting. This wall was built in 1772 by Court Officer Nguyen-Cuu-Dam. It extended past the boundary of this detail map, followed the river and smoothly  turned toward 300 degree direction, toward the current (2016) train terminal in Hoa-Hung, then turned sharply toward 225 degree direction to the (ancient) Cay-Mai Pagoda at the intersection of Hong-Bang street and Nguyen-Trai street. The fighting wall was 8km long and was built by the Vietnamese Court Officer Nguyen-Cuu-Dam.

There is also another “Luy-Cat-Ngang”, wall for fighting which cuts across the field. Part of this fighting wall is over Binh-Long street, near the round about with 6 streets including Binh-Long, Thoai-Ngoc-Hau and Au-Co.

The current street of Luy-Ban-Bich (in sub-District Tan-Thanh, District Tan-Phu, Saigon) is between the locations of two ancient fighting wall and is NOT anywhere near the “Ban-Bich-Co-Luy” it wants to honour. The street honoring Court Officer Nguyen-Cuu-Dam is also NOT anywhere near his celebrated “Ban-Bich-Co-Luy”.

It is found in the original map by Court Officer Nguyen-Cuu-Dam that prior to the year 1790, Saigon area had been surrounded by a multitude of rivers, streams and Vietnamese dug canals. The area was thus well drained in that time. Planning schemes after 1975 did not pay much attention to this fact and created a flood prone city.

It is also seen in this map that current main streets are built on top of ancient (1700’s) roads/streets or Vietnamese dug communication canals. The alignment of current city streets in the direction of North-East and South-East is due to the planning before the year 1790.

3. Map of the second and last Saigon Citadel (1836-1859).

When the Governor Le-Van-Duyet of Gia-Dinh killed the father of a mistress of the 2nd Nguyen King, the King got upset. After the Governor died of natural death, he was posthumously trialed and convicted. His adopted son and followers revolted against the King. Few years later they lost and 1500+ of them were executed. The first Citadel was demolished by the King’s force in 1836. The King then built a second, smaller Citadel at the North corner of the large previous Citadel.

SaigonThanhPhung-GiaDinh

Figure: Overlay of an old map drawn in 1815 on current Open Street Map.

Original 1815 map by Tran-Van-Hoc has no copyright. Annotated map by Trinh-Hoai-Duc in Gia Dinh Thanh thong chi, in Viet Nam Nhat Thong Chi, Quoc Su Quan Vietnam has no copyright. Open Street Map data are used under Open License. Open Street Map data are owned by Open Street Map Contributors (see website www.openstreetmap.org).

This second citadel looks like a fortress guarding against attacks in any direction. However it was inadequately equipped to resist the attack by a modern equipped alliance by France and Spain. After the fall of Gia-Dinh Citadel, the French left the wall structure alone until 1859. The wall structure can be seen in French drawn maps until 1859.

It is seen in this map that many current main streets are built on top of ancient (1700’s) roads/streets or Vietnamese dug communication channels. Many of the Vietnamese dug water routes have been turned into surface routes.

We have to wonder how rain water escapes in the year 1859.

4. Conclusions

The ancient maps align remarkably well to the modern satellite maps; it was a remarkable feat by people at that time. The streets of Saigon seem to have been laid out since ancient time. The current flooding of the city is a result of human change to natural landscape and may not be a small problem.

References.

1.Tran Van Hoc (1815), Plan de Gia-định et des environs, dressé par Trần-văn-Học, le 4e jour de la 12e lune de la 14e année de Gia-Long-1815.

2. Trinh Hoai Duc, Gia Dinh Thanh thong chi, Dai Nam Nhat Thong Chi, Vietnam Quoc Su Quan. (year ?)

3. Petrus Ky, Souvenir historique sur Saigon and ses environs.

4. Anonymous authors, Hinh Anh Viet Nam xua & nay, Hinh Anh Viet Nam xua & nay, http://hinhanhvietnam.com/ban-do-sai-gon-xua/, accessed Mar. 2016.

5. Mai Tran, Kể chuyện kinh cầu xưa vùng Sài Gòn Chợ Lớn trước 1975 (P1), maivantran.com, http://maivantran.com/2013/11/19/ke-chuyen-kinh-cau-xua-vung-sai-gon-cho-lon-truoc-1975-p1/, posted

6. Nguyen Tien Quang, Bản đồ Việt nam xưa, http://www.nguyentienquang-huongtram.blogspot.com,  http://www.nguyentienquang-huongtram.blogspot.com/2013/11/ban-o-sai-gon.html, posted 17 No. 2013.

7. James M. Haley, 1861 French Conquest of Saigon: Battle of the Ky Hoa Forts, Historynet.com, http://www.historynet.com/1861-french-conquest-of-saigon-battle-of-the-ky-hoa-forts.htm. posted 6 Dec. 2006.

8. James M. Haley, 1861 French Conquest of Saigon: Battle of the Ky Hoa Forts, Vietnam Magazine, June 2006 .

Click here for my other blogs.

divider43.jpg

polymeraust100dollars

Click here for all my blogs

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

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