Hi all,
In running some largish vector calculations that involved calculating population, using areas overlaid with Australian Census Collection districts (which have up to 12,000 areas), I've noticed a couple of issues with the above modules.
v.overlay - Is leaving a lot of "orphan" lines ("incorrect boundaries") when a large map is overlaid with a much smaller map. This doesn't affect calculation much, but it does affect display.
If I were only working with a few target areas, I could use v.digit to correct the result, but with a large and complex map the job is rather daunting!
v.distance - when using the -a option (measure distance to all areas in boundary), it cannot create the database table for to_attr outputs.
example from Spearfish:
v.distance from=bugsites from_type=point to=archsites to_type=point -a upload=dist,to_attr column=dist,character to_column=str1 table=test2
100%
DBMI-DBF driver error:
Column 'dist' already exists (duplicate name)
Cannot create table.
Error in db_execute_immediate()ERROR: Unable to create table: 'create table test2 (from_cat integer, dist
double precision, dist double precision )'
or, if I alter the column order:
v.distance from=bugsites from_type=point to=archsites to_type=point -a upload=to_attr,dist column=character,distance to_column=str1 table=test2
100%
DBMI-DBF driver error:
SQL parser error: syntax error, unexpected ',', expecting NAME processing ','
in statement:
create table test2 (from_cat integer, , distance double precision )
Error in db_execute_immediate()ERROR: Unable to create table: 'create table test2 (from_cat integer, ,
distance double precision )'
Cheers,
Richard Chirgwin