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GRASS 6 Tutorial/Vector spatial analysis

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< GRASS 6 Tutorial

Contents

1 Vector Spatial Analysis

1.1 Vector Union

1.2 Vector Intersection

1.3 Vector Clip

2 Vector Analysis using the GUI

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 (http://grass.osgeo.org/grass64/manuals/v.overlay.html) , which can either be run using the GUI

or from the command-line interface. The following examples are demonstrated using the CLI, using two

vector datasets, namely: urbanarea and census_wake2000 from the North Carolina database.

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 (operatoror) of the two polygon vectors:

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

with urban_census2000 created as follows.

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Vector Intersection

The following command creates an intersection (operatorand) 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 (operatornot) of the two polygon vectors:

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

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Vector Analysis using the GUI

The above examples can be easily replicated using the v.overlay GUI, available underVector --> Overlay

Vector Maps --> Overlay Vector Maps [v.overlay]. The default tab allows you to select the two vector files

(ainput and binput):

The second tab ('Optional') allows you to specify the vector operator (or, and, not, ...) as well as other

options:

Once you have made your selections, simply clickRun

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Content is available under GNU Free Documentation License 1.2.

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