Geographic Information Systems (GIS) are mainly used for creating digital vector images (maps) with an underlying data table. However, GIS can also be used to create raster images. For example, an altitude map can be generated based on input in GIS. A raster image generated in GIS can be further formatted with a color scheme. Such a GIS raster image is often called a grid.

Preferred formats 

• ASCII GRID (.asc, .txt)

Non-preferred formats

• Esri GRID (.grd and associated files)
• Surfer Grid (.grd; .srf)
• ERDAS IMAGINE File Format (.img)