[GRASSLIST:5709] Re: Creating DTM from shapefiles

[Moritz Lennert]

On Thu, February 10, 2005 13:05, Māris Nartišs said:
> Hi,
>
> Seems, that joining two vector data sets (shapefiles) in Grass is
> "mission impossible".
>
>> What happens if you append 2 files with attribute tables that have different
>> formats?
> Actualy for me, lamer, they look like same:
>
> v.db.connect map=augstump driver=dbf
> database=/home/maris/Test_in_grass/testlocation/testmapset/dbf/
> key=cat layer=1 -c
> INTEGER|CAT
> DOUBLE PRECISION|AUGST
>
> v.db.connect map=izol_p driver=dbf
> database=/home/maris/Test_in_grass/testlocation/testmapset/dbf/
> key=cat layer=1 -c
> INTEGER|CAT
> DOUBLE PRECISION|AUGST
>
>
> And v.append error:
>
> v.append vect1=augstump vect2=izol_p vmerged=augstump_izol_p
> vtype=point vlayer=1
> Exporting 74 points/lines...
> 74 features written
> Exporting 172640 points/lines...
> 172640 features written
> Datum 'unknown' not recognised by GRASS and no parameters found. Datum
> transformation will not be possible using this projection information.
> Over-riding projection check.
> Proceeding with import...
> Layer: augstump_izol_p
> DBMI-DBF driver error:
> Column 'CAT' already exists (duplicate name)

It seems to try to create a table containing all columns from the original two
tables. Try renaming the columns of one of the tables to CAT2 and AUGST2 and
see what happens.


> Cannot create table.
> Error in db_execute_immediate()
> Cannot create table: create table augstump_izol_p (cat integer, CAT
> integer, AUGST double precision)
>
> _______________________________________
> I know what I want, but duno how to get it.
> My idea: 2 vect. data sets with 2 dbs. Take first of them, get max cat
> num. Take second one and increase cat by first max cat num. Append
> second to first w/o problems (ie. cat 2 >> 1), cuz cat nums not
> owerlap. Wola. One data set containing data from both input sets.
> Is it possible in Grass? Or I need to start to study ArcInfo?


If the above suggestion works, you could then use simple SQL to populate one
CAT column with unique cat nums.

Moritz