I am currently working on a project where I need a geological map of Africa for groundwater potential. I have downloaded the Surficial geology of Africa from the U.S. Department of Interior (map URL). I need assistance on how to interpret the data.


This is not an answer.

I downloaded the "geo7_2ag.zip", unzipped it, ran ogrinfo -al on the geo7_2ag.shp file and learned the following:

  • The shapefile contains 11,977 polygons, each tagged with a GLG value.

  • There are 44 different GLG values. Some of these are: DS, H2O, Mi, O, S_d

  • Most of these values are explained in geo7_2ag.shp.xml and appear to represent geological eras. For example, "DS" means "Devonian-Silurian", "H2O" means "Water (River or Lake)", "Mi" means "Mesozoic Igneous", and so on.

  • The data is imperfect. The "Cm" and "O" values in the shapefile are not in the XML file. The "JI" and "KI" values are spelled with a capital "eye" in one of the files and a lower case "ell" in the other.

  • The geo7_2ag.e00 contains 4 layers of data:

    • an "ARC" layer with 25,285 line strings

    • a "CNT" layer with 11,978 points

    • a "LAB" layer with 11,977 points

    • a "PAL" layer with 11,977 polygons

According to https://gis.stackexchange.com/questions/54730/e00-file-structure these data layers are intended primarily to transfer data between formats and are probably not important for you, the end user.

As a general note, gis.stackexchange.com might be able to help more with further questions, and you might look into qgis, a free tool to help interpret and manipulate geographical data.

  • This actually seems like a pretty good answer. They asked for help interpreting the data, and that's what you did here. – csk Nov 14 '19 at 17:44
  • Thanks for this response. – Abbey Tope Nov 16 '19 at 1:46

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