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.