[GRASS-user] area calculation after dissolve

[Uwe Fischer]

I have a polygon dataset which needs to be dissolved by a certain item. That
works fine. But when I calculate the area size for the new created Polygons
in the next step using v.to.db, I find that the system summarizes all the
polygons with the same value in the dissolve item, even if they are remote
from each other (I mean, they do not touch). That might be correct if I want
to handle them like a multipart feature, but those are not present in GRASS
as far as I know. What I need is the area for each single polygon after
removing the inside borders, no matter what value the polygon has. How to
calculate that?

I found that polygons with the same dissolve item also have the same cat
number, which might be the reason for the common area size. But I don't know
how to clear that without losing the connection to the database table
containing the dissolve item.

 

Best regards,

 

Uwe

 

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