[GRASS-user] v.overlay and points?

[Nikos Alexandris]

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
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