GRASS 6 Tutorial/Vector spatial analysis

Vector Spatial Analysis

The following examples demonstrate how basic vector data processing operations, such as overlay, union and clipping can be performed in GRASS 6.4. These operations are all performed using the GRASS module, v.overlay For the purposes of these examples, the two datasets that we will use are urbanarea and census_wake2000. All examples are created using the vector datasets in the North Carolina database.

Zoom of input datasets

d.mon start=x0
g.region vect=census_wake2000 
d.vect census_wake2000 col=blue
d.vect urbanarea col=red type=boundary

Vector Union

The following command creates a union (operator or) of the two polygon vectors:

v.overlay ain=census_wake2000 bin=urbanarea out=urban_census2000 operator=or

with urban_census2000 created as follows.

Vector Intersection

The following command creates an intersection (operator and) of the two polygon vectors:

v.overlay ain=census_wake2000 bin=urbanarea out=urban_census2000_intersect operator=and

Vector Clip

The following command clips (cuts out) intersection (operator not) of the two polygon vectors:

v.overlay ain=census_wake2000 bin=urbanarea out=urban_census2000_intersect operator=not