[GRASS-dev] [GRASS GIS] #1654: v.extract: allow direct transformation of centroids to polygons
#1654: v.extract: allow direct transformation of centroids to polygons
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Reporter: mlennert | Owner: grass-dev@…
Type: enhancement | Status: new
Priority: normal | Milestone: 7.0.0
Component: Default | Version: unspecified
Keywords: |Platform: Unspecified
Cpu: Unspecified |
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A recurrent task is to extract centroids from polygons and to use them as
points in further analysis. Currently, one has to do this in two steps:
{{{
v.extract in=polygonmap out=centroidmap type=centroid
v.type in=centroidmap out=pointmap type=centroid,point
}}}
As this is IMHO such a basic operation, it would be great if v.extract
could directly create a point layer. This could be implemented in
different ways (in my order of preference):
1) If map contains polygons, but no points and type=point is given, then
extract the centroids as points, if type=centroid extract as centroids.
2) If type=centroid is given, extract as points by default, but allow to
extract as centroids by use of a flag
3) If type=centroid is given, extract as centroids by default, but allow
to extract as points by use of a flag
A problem obviously might occur if a map contains a mix of polygons and
points...
Moritz
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Ticket URL: http://trac.osgeo.org/grass/ticket/1654
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[GRASS-dev] Re: [GRASS GIS] #1654: v.extract: allow direct transformation of centroids to points (was: v.extract: allow direct transformation of centroids to polygons)
#1654: v.extract: allow direct transformation of centroids to points -+-- Reporter: mlennert | Owner: grass-dev@… Type: enhancement | Status: new Priority: normal | Milestone: 7.0.0 Component: Default | Version: unspecified Keywords: |Platform: Unspecified Cpu: Unspecified | -+-- -- Ticket URL: http://trac.osgeo.org/grass/ticket/1654#comment:1 GRASS GIS http://grass.osgeo.org ___ grass-dev mailing list grass-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-dev
[GRASS-dev] Re: [GRASS GIS] #1654: v.extract: allow direct transformation of centroids to points
#1654: v.extract: allow direct transformation of centroids to points -+-- Reporter: mlennert | Owner: grass-dev@… Type: enhancement | Status: new Priority: normal | Milestone: 7.0.0 Component: Default | Version: unspecified Keywords: |Platform: Unspecified Cpu: Unspecified | -+-- Comment(by hamish): do one thing well and don't duplicate or blur functionality. to perform multiple actions at once write a wrapper script. thanks, Hamish -- Ticket URL: https://trac.osgeo.org/grass/ticket/1654#comment:2 GRASS GIS http://grass.osgeo.org ___ grass-dev mailing list grass-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-dev
[GRASS-dev] v.net.salesman tour optimization
Hi all, in grass7 addons [0], there is a new version of v.net.salesman with optional tour optimization. The current algorithm to find the shortest tour is heuristic and often does not find the optimal tour for more than 10 nodes to visit. The optimization methods available are bootstrapping and a genetic algorithm, both of which provide a better result (shorter tour) than the original method. Both optimization methods are rather crude an brute force, but better than nothing and sometimes get close to the known optimal tour for up to 1000 nodes. Testing welcome! Markus M [0] https://svn.osgeo.org/grass/grass-addons/grass7/vector/v.net.salesman.opt/ ___ grass-dev mailing list grass-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-dev
[GRASS-dev] Re: [GRASS GIS] #1654: v.extract: allow direct transformation of centroids to points
#1654: v.extract: allow direct transformation of centroids to points -+-- Reporter: mlennert | Owner: grass-dev@… Type: enhancement | Status: new Priority: normal | Milestone: 7.0.0 Component: Default | Version: unspecified Keywords: |Platform: Unspecified Cpu: Unspecified | -+-- Comment(by hamish): sorry if that came out harsh, I was in a hurry and meant to be brief, but not curt. option 3 is the most acceptable to me, but even then I'd open access to it with a lot of caution. Remember that the absolute position of a centroid is just somewhere within the area, it is not guaranteed to be in the middle, so users must be very careful treating them as points with absolute x,y,z meaning. e.g. C, O, L shaped areas; areas created by v.buffer or v.overlay may have centroids may have their centroids right near an outside edge; etc. I'm not sure how you are using it, but fwiw see also the add on module v.points.cog: v.points.cog is a shell script which will create a new point at the center of gravity of each cluster of input points or centroids, grouped by attribute. Among other things this is useful for labeling swarms of points. regards, Hamish -- Ticket URL: https://trac.osgeo.org/grass/ticket/1654#comment:3 GRASS GIS http://grass.osgeo.org ___ grass-dev mailing list grass-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-dev
[GRASS-dev] Newbie question
All, I am a benched developer at an IT contracting company looking to help out on an open-source project. I primarily work with Java but understand C pretty well. Would any of you have any suggestions on how I could contribute to this project? Owen Brown Developer Catalyst IT Services ___ grass-dev mailing list grass-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-dev
Re: [GRASS-dev] Newbie question
Hi Owen, This page [0] is a good entry point, Pierre [0]: http://grass.osgeo.org/wiki/Development 2012/5/15 Owen Brown obr...@catalystitservices.com: All, I am a “benched” developer at an IT contracting company looking to help out on an open-source project. I primarily work with Java but understand C pretty well. Would any of you have any suggestions on how I could contribute to this project? Owen Brown Developer Catalyst IT Services ___ grass-dev mailing list grass-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-dev -- Scientist Landcare Research, New Zealand ___ grass-dev mailing list grass-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-dev
