GRASS GIS for ArcGIS users

Projections

ArcGIS supports on-the-fly projection of spatial data while GRASS GIS considers this as a bad practice and requires user to have consistent projection for all the data entering the analysis.

Data, databases and file formats

In ArcGIS, users often have data in different directories on disk. GRASS GIS sets a specific system to organize the data. First, data must be in one directory called GRASS GIS database directory. You can have one or more of these directories on your disk. This directory contains GRASS Locations. All data in one Location have the same projection (coordinate system, datum). Location is a directory which contains GRASS Mapsets. Mapset contains raster and vector maps (layers) and other geospatial data.

Cartography

The standard display in GRASS GIS

3D visualization

In GRASS GIS, the 3D view is integrated into the main graphical user interface (GUI) while in ArcGIS suite, there is a separate tool ArcScene. The GRASS GIS library which is behind the 3D view is called NVIZ. The integration of NVIZ into GUI which is called wxGUI is called wxNVIZ. The 3D visualization is also available as a module called m.nviz.image (usable from command line or Python).

In GRASS GIS, when you are in 2D and you switch to 3D, all raster map layers are automatically added to the 3D view as surfaces. This means that if you have in 2D a digital elevation model, you will see it as a 3D visualization of terrain in 3D. The colors set will be the same colors as in 2D. This is different from ArcScene where the raster layer is initially flat and you have to specify in properties which raster should be used to create the surface.

See also

• Terminology comparison between ArcGIS and GRASS GIS
• Tips for Arc users
• GRASS migration hints
• Performance comparison GRASS vs. ArcGIS