On 23/04/12 20:16, Rich Shepard wrote:
I have a few dozen points to add to a vector map and can do this most
easily using the SQL 'INSERT INTO ...' syntax directly on the postgres
table. Does GRASS automagically update the cat column, or do I do this as
part of the insert statement?
As others have already said, you have to differentiated between the
insertion of the geometry (i.e. the point) and the insertion of
attribute information.
For the insertion of new points into an existing map, GRASS offers
different solutions:
- v.digit for manual digitalisation of points
- v.edit tool=add (using a text file or standard input with points given
in GRASS ascii standard (not point !) format)
- v.in.ascii + v.patch
In terms of attributes, if your new points have the exact same
attributes as the existing points, v.in.ascii + v.patch is probably the
easiest: just put your points into a csv file with all attributes, use
the columns= parameter of v.in.ascii to correctly define the columns so
that they match the existing ones, drop the x and y columns after import
with v.db.dropcol and then v.patch the newly imported points into the
existing ones, using the -e flag to keep the attributes. You can also
use the -a flag of v.patch to append the data into the existing map.
If you have added points with categories (e.g. through v.edit), but
without an entry in the table, you can then just insert an entry with
just a category number into the attribute table with v.to.db and then
add the values into the other attribute columns with v.db.update. Or you
can just insert everything (category value included) with a standard
INSERT INTO statement.
I guess a "existing map to which data should be appended" parameter in
v.in.ascii / v.in.ogr would be nice.
Moritz
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