[GRASS-user] GRASS used for energy calculations

GRASS GRASS user
1

Hi,

starting from a discussion in the gfoss.it mailing list, I have compiled
some material about GRASS used for energy calculations:
http://grass.osgeo.org/wiki/Energy_calculations

please add more...
Markus

2

Hi,

I have some troubles with understanding v.category.

I have a map with the road network. After using v.clean, I have lines with the same cat. Now I want to give each line a unique cat going from 1 to N, and then add 4 columns with the coordinates of the start and end coordinates of each line.

So I did use:
v.category input=roads output=roads_nocat option=del
for removing the categories.

I did also remove all database entries using
echo "DELETE FROM roads_nocat" | db.execute
which deletes all rows but leaves the table in the database (using the default DBF database)

and then I did add the categories again using:
v.category input=roads_nocat output=roads_cat option=add

There are still some lines sharing the same cat...

As a consequence, if I call then:
v.db.addcol map=roads_cat columns='startx DOUBLE PRECISION, starty DOUBLE PRECISION'
v.to.db map=roads_cat option=start columns=startx,starty
I get logically a warning for the lines sharing the same cat

Is this normal behaviour? What did I wrong? Sorry if I am missing something obvious.

Christian