Does a database or dataset exist that lists all exact Degrees, Minutes, and Seconds (rounded to nearest decimal) for the continent of South America? What I am seeking is a list of DMS's that covers that entire geography; not just a few specific coordinates, but all of them. Given that each DMS represents ~60 nautical miles apart, the data shouldn't be overly complicated to form. The trouble is, I can't locate the consolidated data anywhere on the web!


Outline solution:

  • Get boundary data for all countries in the region (can be downloaded from gadm.org)

  • Loop over all D/M/S on the earth, doing point-in-polygon tests over the boundary data from step 1 - this can be done using Python, R, Java or C or lots of other programming languages.

  • Keep those D/M/S values that are inside the boundaries.

How many points would you expect? The whole earth is 360 degrees round and 180 degrees north-south, so thats 360*60*60 * 180*60*60 = 8.4 x 10^11 points. South America is maybe 1/10 of the planet, so that's about 10^10 points - a few billion.

You'll end up with a table of a few billion points. I'm not sure how that would be useful, but that's how you'd do it.

  • I opted to use QGIS3 with the imported GADM.org boundary layer for the Earth. With the boundary layer correctly placed in the "layers" section of QGIS3, I then created a custom polygon shape. From there, I attempted to use the "Count Points in Polygon..." feature followed by the "Open Attribute Table" to collect the desired D/M/S values. Unfortunately, the resulting table indicates that there are zero points present within the polygon shape. – ScienceGuy Oct 28 '18 at 20:19
  • Did you first create a grid of DMS points over your study area? – Spacedman Oct 28 '18 at 20:46
  • I did not. The reason being is that I don't know the D/M/S points. The collection of the points was intended to come from the GADM.org data, or so I thought. How can I create a grid of points if the points are unknown at the time of capture? – ScienceGuy Oct 28 '18 at 22:11
  • In my outline you first generate a grid of DMS points over the whole earth. You can also generate a grid of points that span a vector layer in QGIS with one of the vector processing algorithms – Spacedman Oct 28 '18 at 23:01
  • Thank you for the further replies, Spacedman. I followed that outline (which was very much appreciated), but I'm still unclear on how to access the DMS points with which to generate the grid--the grid part I understand, as well as all points thereafter. How does one present/collect (for lack of a better word) the DMS points from the GADM.org data in the first place? – ScienceGuy Oct 29 '18 at 0:17

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