Im trying combine 2 vector maps, one with areas, the other with solely points.
V.overlay fails with any file that only has points, is there any way around this?
I was thinking of changing the point to an area , ie 1x1 meter, to work around this limitation, but Im not certain if this is possible or advisable. Does anyone have any ideas?
Thanks!
Charlie
Hello Charlie,
v.what.vect might be the function you need. Have you tried that?
Success!
Miguel
2013/3/19 charlie <carowan@yahoo.com>
Im trying combine 2 vector maps, one with areas, the other with solely points.
V.overlay fails with any file that only has points, is there any way around this?I was thinking of changing the point to an area , ie 1x1 meter, to work around this limitation, but Im not certain if this is possible or advisable. Does anyone have any ideas?
Thanks!
Charlie
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user
Hi,
On Monday 18 of March 2013 20:14:54 you wrote:
Im trying combine 2 vector maps, one with areas, the other with solely
points.
[..]
It is not possible to use v.overlay on "points" AND "areas". Check the manual:
<http://grass.osgeo.org/grass64/manuals/v.overlay.html>\.
Maybe you simply want to merge the two vector maps? In that case, v.patch
will do it.
Best, Nikos
Nikos, Thanks for the reply.
Will v.patch merge the attribute table so all of the data will be combined together in a new attribute table?
I am trying to merge 2 files, one with plot and address info (area) and the second with property owner info (point). Both of these files contain information about the the plot of land hence they precisely overlay each other, but neither contain any data, besides geography,that can be used to merge the files.
Charlie
From: Nikos Alexandris nik@nikosalexandris.net
To: charlie carowan@yahoo.com
Cc: “grass-user@lists.osgeo.org” grass-user@lists.osgeo.org
Sent: Tuesday, March 19, 2013 4:58 AM
Subject: Re: [GRASS-user] v.overlay and points?
Hi,
On Monday 18 of March 2013 20:14:54 you wrote:
Im trying combine 2 vector maps, one with areas, the other with solely
points.
[…]
It is not possible to use v.overlay on “points” AND “areas”. Check the manual:
<http://grass.osgeo.org/grass64/manuals/v.overlay.html>.
Maybe you simply want to merge the two vector maps? In that case, v.patch
will do it.
Best, Nikos
charlie wrote:
Will v.patch merge the attribute table so all of the data will be combined
together in a new attribute table?
Well, if both (all) original tables are identically structured, you may use
the "-e" flag to copy over the attribute tables. In the case of points and
boundaries I guess you don't need to v.clean afterwards (not sure though -- it
is something users *should* do after merging for example overlapping/duplicate
features).
If your tables are different, then you'd need to handcraft I guess the table
(again!). First you'd need to add the table of the "patched" map in the
database (it is not added, so one requires to instruct v.db.addtable) and then
add columns (v.db.addcol -- or v.db.addcolumn for GRASS7) and populate them as
desired (v.to.db).
I am trying to merge 2 files, one with plot and address info (area) and the
second with property owner info (point).
If the points refer to the plots I think your better off by using the GRASS
approach: an area consists of boundaries and centroids. You may then use the
boundaries for area statistics and still have the centroids to use for point-
like tasks (?).
(
Please, do not take for granted what I state -- I am recovering slowly in to
all this as I was absent for a long time. I feel much more confident in the
raster planet than in the vector planet since my last work was mainly on
raster stuff.
)
Both of these files contain information about the the plot of land hence they
precisely overlay each other, but neither contain any data, besides
geography, that can be used to merge the files.
Maybe that fits the picture then -- boundaries and centroids.
Please, review the following which, I think, are of your interest:
- <http://grass.osgeo.org/grass64/manuals/vectorintro.html>
- <http://grass.osgeo.org/grass64/manuals/databaseintro.html>
One thing is for sure: you have in GRASS all the tools you might need for
processing "plots" 
Best, Nikos
Nikos
On Tuesday 19 of March 2013 19:57:36 Nikos Alexandris wrote:
charlie wrote:
..
> Both of these files contain information about the the plot of land hence
> they precisely overlay each other, but neither contain any data, besides
> geography, that can be used to merge the files.
Then again, you may only require to add centroids to the "plot" map?
Something like
v.centroids in=OnlyBoundariesMap out=Plots option=add
Check however the "cat=" parameter (what and how).
Best of Luck, Nikos
On Tue, Mar 19, 2013 at 2:50 PM, charlie <carowan@yahoo.com> wrote:
Nikos, Thanks for the reply.
Will v.patch merge the attribute table so all of the data will be combined
together in a new attribute table?I am trying to merge 2 files, one with plot and address info (area) and the
second with property owner info (point). Both of these files contain
information about the the plot of land hence they precisely overlay each
other, but neither contain any data, besides geography,that can be used to
merge the files.
That sounds more like a job for v.distance where you can upload
attributes from the nearest feature in map B to Map A. In GRASS 6 you
can upload area info to the points, in GRASS 7 you can also upload
point info to the areas.
HTH,
Markus M