[GRASS-user] Problem using allpairs for spatial analysis

דור פרידמן dof1985 at gmail.com
Wed Apr 3 13:43:45 PDT 2013

Hello all,

I'm trying to calculate a matrix of all shortest paths from settlements to
3 types of waste treatment facilities.

My methodology is to use the following layers:
1. roads - lines.
2. poi - points (combination of 3 layers as follows):

I used 3 distinct layers - landfill sites, recycling sites and sites which
preforms both landfilling and recycling. I combined them to one layer
called poi and uses v.db.update to change the categories of each layer. The
reason for this is that those 3 layers was extracted out of one "sites"
layer and their cats are messed up. I need to separate them since I would
like to analyze each distance matrix separately.

I changed the cats by summing 10000 + cat, 20000 + cat and so on, for each
type of site, including the settlements. Afterwards I plan to filter and
extract from this layer the following maps:

allpairs - settlements to landfill, settlements to recycling and
settlements to both. Than I'll use excel to add gate fees to transportation
costs and to find the cheapest route from each settlement to one site in
each category.

The problem is that after doing allpairs, I have received in both from and
to cat the original cats and not those that I changed with v.db.update.

i.e. before all pairs poi cats would look something like that:

cat = 10133, name, type=1
cat = 40121, name, type=4

after allpairs it became something like that:
cat=1, from_cat=133, to_cat=121 and so on...

How can it be fixed?


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