A gazetteer is a list of place names and their coordinates. The files you can download here are for use in DIVA for automatic georeferencing (to assign coordinates to places). The files should be placed in the \\gazet directory. This is very old now. There area better services for this.
DBF
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Formats
The files have been compressed and grouped in ZIP files. You can use programs such as 7-zip, PKZIP or StuffIt to decompress the files.
Vector data are stored as ESRI shapefiles
Grid (raster) data are stored as DIVA gridfiles
Each "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. It can be imported to most other GIS programs. Shapefiles contain a single class of "vector" data such as points, lines, or polygons.
Gridfiles are used in DIVA-GIS. From DIVA-GIS they can be exported to a number of other grid formats including IDRISI and Arc or to shapefiles.
A gridfile with "country mask" indicates that the areas outside the selected country are masked out. For these areas, the value is "NODATA" (indicating the absence of data for those cells). For the other gridfiles, NODATA is only used for areas covered with water, except for the land cover grids, on which water is a separate class.
A DBF (dBase file) is a dbase format database table.
Resolution
The resolution is the size of each grid cell expressed as the length of one side of one (square) cell. The units are in (arc) degrees, minutes or seconds. When the cell size is small (e.g., 30 seconds), resolution is high. The size in square meters varies with latitude. A cell with a 30 seconds resolution is about 0.8 km2 at the equator and smaller at higher latitudes. High resolution files for large areas (countries) can be very large. This means that it may take a while to download these files, and that you will need a fast PC to work with them.