The coordinate reference system is latitude/longitude and theWGS84 datum.
File Formats
A "shapefile" consist of at least three actual files. This is a commonly used format that can be directly used in Arc-anything, DIVA-GIS, and many other programs. Unfortunately, non-latin characters are garbled.
An "ESRI geodatabase" is an MS Access fole that can be opened in ArcGIS (an expensive but powerful program). One of its advantages, compared to a shapefile, is that it can store non-latin characters (e.g. Cyrillic and Chinese characters).
A "Google Earth .kmz" file can be opened in Google Earth.
A "RData" file can be used in R (with the sp package loaded)
Some files have been compressed and grouped in ZIP files. You can use programs such as 7-zip, PKZIP or StuffIt to decompress the files. The coordinate reference system is latitude/longitude and theWGS84 datum.
GADM database of Global Administrative AreasGADM is a spatial database of the location of the world's administrative areas (or adminstrative boundaries) for use in GIS and similar software. Administrative areas in this database are countries and lower level subdivisions such as provinces, departments, bibhag, bundeslander, daerah istimewa, fivondronana, krong, landsvæðun, opština, sous-préfectures, counties, and thana. GADM describes where these administrative areas are (the "spatial features"), and for each area it provides some attributes, foremost being the name and variant names.
The current version is 1.0
The data are available as shapefile, ESRI geodatabase, RData, and Google Earth kmz format. Shapefiles can be used for most mapping and "GIS" software (you can download a free program such as Q-GIS or DIVA-GIS. The RData files can be used in R with the 'sp' package loaded.
Here is more information on formats and their limitations.
You can download country level files (recommended) or files covering the entire world
Our goal is to map all administrative areas of all countries, at all levels, at any time period. We use a high spatial resolution, and of a extensive set of attributes for each spatial feature. This is a never ending project, but we are happy to share what we have so far. The current version of GADM maps 226,439 administrative areas (or 167,176 if you count only the lowest level for each country). You can see them on these maps.
Our intention is to transform this project into a global collaborative effort. We still need to work out the best way of organizing this. But please contribute in whatever way you can by sending us a message to point out errors, or even better, to send an improved file for a country of your interest.