[GRASS-user] How To update attribute based on intersection?

Roger André randre at gmail.com
Fri Dec 11 12:45:25 EST 2009


Hi All,

I'm having trouble finding the solution to this in the "GRASS Book",
what I've found so far creates a new data set as the result of an
intersection.  What I would like to do instead is update the value of
an attribute based on whether the feature in that vector layer
intersects with those in another vector layer.  Is that possible?

In PostGIS the operation looks like:

UPDATE data_set_1 SET foo = 1 FROM data_set_2 WHERE
ST_Intersects(data_set_2.the_geom, data_set_1.the_geom);

While this works in PostGIS, it's slow.  I'd like to see if it can be
done more quickly in GRASS.

Thanks in advance for any assistance you can provide,

Roger
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