The US Army Map Service (AMS) was the military cartographic agency of the United States Department of Defense from 1941 to 1968, subordinated to the United States Army Corps of Engineers. The major task of the Army Map Service was the compilation, publication and distribution of military topographic maps.
https://en.wikipedia.org/wiki/Army_Map_Service
1:250K scale (1cm on map = 2.5km on ground) AMS maps for India, each covering an area of 1.5″x1″ or 167x111km can be downloaded from the link below. See Image 2 below
https://maps.lib.utexas.edu/maps/ams/
AMS maps are compiled based on existing Survey of India maps prepared as part of the Great Trigonometric Survey and are topographic map with 500ft contours. See Image 3 below.
Let’s download AMS map “ni-43-15” and geo-reference the same in QGIS using CRS EPGS 43:26 – WGS-84. See Image 4 below.
Comparison
To verify whether we have correctly geo-referenced the AMS map we can compare it with a standard “OpenTopoMap” base map. Overlay the AMS map 50% transparent over the base map to compare if the terrain features are matching. Similarly we can do a side-by-side wise comparison of both (hiding each one in turn). See Image 1+2 below.
Image 3 below shows an area-wise coverage comparison between an AMS (left), Olizane (right), Soviet (center) and Survey (center-bottom) maps in QGIS. Image 4 below compares the detail of a 1:50K Survey, 1:150K Olizane, 1:100K Soviet and 1:250K AMS maps. Higher scale (1:50K) corresponds to finer detail.
Assignment
Acknowledge your understanding of the concepts learned in this module by downloading and geo-referencing AMS map “ni-43-15” and comparing with the other maps in this chapter.
