[GRASS-user] Two questions - vector data and Mac install

GRASS GRASS user
1

Hi all,

1) v.overlay question

I have three maps: two area vectors (A and B), and a v.overlay result (C). Is there a simple way to assign the percentage of areas in (A) covered by the overlay (C)?

2) Mac install

Wish 8.4 is breaking on a friends new installation, with the reason as "image not found". Do we need to reinstall X or is it something else?

Richard Chirgwin

2

Hi,

Hi all,

1) v.overlay question

I have three maps: two area vectors (A and B), and a v.overlay result
(C). Is there a simple way to assign the percentage of areas in (A)
covered by the overlay (C)?

What I think of in a rush is to rasterize the areas first and afterwards asking
for the overlapping areas in percent with r.stats -a input=map1,map2

Regards,
Christian.

2) Mac install

Wish 8.4 is breaking on a friends new installation, with the reason as
"image not found". Do we need to reinstall X or is it something else?

Richard Chirgwin
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grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user

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3

Christian Schwartze wrote:

Hi,

Hi all,

1) v.overlay question

I have three maps: two area vectors (A and B), and a v.overlay result
(C). Is there a simple way to assign the percentage of areas in (A)
covered by the overlay (C)?
    
What I think of in a rush is to rasterize the areas first and afterwards asking
for the overlapping areas in percent with r.stats -a input=map1,map2

Regards,
Christian.

Christian,

Thanks, I will give this a try.

By the way, install fixed, somehow Mac OSX X got lost ...

RC

2) Mac install

Wish 8.4 is breaking on a friends new installation, with the reason as
"image not found". Do we need to reinstall X or is it something else?

Richard Chirgwin
_______________________________________________
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user

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This mail was sent through http://webmail.uni-jena.de

4

On 25/06/08 02:46, Richard Chirgwin wrote:

Hi all,

1) v.overlay question

I have three maps: two area vectors (A and B), and a v.overlay result (C). Is there a simple way to assign the percentage of areas in (A) covered by the overlay (C)?

Vector solution:

http://lists.osgeo.org/pipermail/grass-user/2008-June/045290.html

Moritz

5

Moritz Lennert wrote:

On 25/06/08 02:46, Richard Chirgwin wrote:

Hi all,

1) v.overlay question

I have three maps: two area vectors (A and B), and a v.overlay result (C). Is there a simple way to assign the percentage of areas in (A) covered by the overlay (C)?

Vector solution:

http://lists.osgeo.org/pipermail/grass-user/2008-June/045290.html

Moritz

Moritz,

This led me straight into an oddity. One of my vectors is created by buffering around points.

The source map was a set of 800 points. V.buffer runs successfully, and when it ends, the new areas display without problem. However, when I run v.db.addtable, there are only 18 categories - any ideas?

Richard

6

On 26/06/08 08:49, Richard Chirgwin wrote:

Moritz Lennert wrote:

On 25/06/08 02:46, Richard Chirgwin wrote:

Hi all,

1) v.overlay question

I have three maps: two area vectors (A and B), and a v.overlay result (C). Is there a simple way to assign the percentage of areas in (A) covered by the overlay (C)?

Vector solution:

http://lists.osgeo.org/pipermail/grass-user/2008-June/045290.html

Moritz

Moritz,

This led me straight into an oddity. One of my vectors is created by buffering around points.

The source map was a set of 800 points. V.buffer runs successfully, and when it ends, the new areas display without problem. However, when I run v.db.addtable, there are only 18 categories - any ideas?

As GRASS is topologically clean, areas cannot overlap. v.buffer, therefore, fusions those buffers that do. So if your 800 points are close enough to each other to make the buffers overlap, they might result in only 18 distinct polygons. This should be visible when you display them.

Moritz