Geospatial Modeling and Analysis


Note: The screenshots were done for GRASS GIS 7.0, there might be therefore slight differences for newer versions of GRASS GIS.


GRASS data structure

For this introduction we create new mapset intro to keep data organized.


GRASS GUI: Add raster map elev_lid792_1m

Set the computational extent and resolution of the mapset to match map elev_lid792_1m. Computational region will be explained later.

Display elevation in 3D view

Display elevation legend

GRASS modules

GRASS functionality is available through modules (tools). Modules respect following naming conventions:

group prefix examples
general g.* g.list, g.remove, g.copy
raster r.* r.univar, r.neighbors, r.contour
vector v.*, v.generalize,
3D raster r3.*,, r3.colors
temporal t.* t.list, t.rast.aggregate, t.vect.univar
... ... ...

Finding and running a module

Type name or keyword in Search:

Raster > Reports and statistics > Basic raster metadata

Type beginning of command in Command console

Command console supports auto-completion of maps and parameters.

Browse command history using up and down arrows.

Region settings

Before we use a module to compute a new raster map, we must set properly computational region. All raster computations will be performed in the specified extent and with the given resolution.
g.region -p

north:      220750
south:      220000
west:       638300
east:       639000
nsres:      1
ewres:      1
rows:       750
cols:       700
cells:      525000

We can set it to match a raster map like this:

Running modules

Module example: r.slope.aspect

Raster > Terrain analysis > Slope and aspect

3D view

Uncheck newly created maps:

Add vector map streams:

Set resolution and map draped over the surface:

Save picture as TIF or PPM file and then quit GUI:

Quit GRASS session