[GRASSLIST:3107] path finding

[Maliheh]

Hello Dear list,

I have written a tcl program that lets users to choose
two points on a road map:
Start point & Destination,
and then grass shows the path on a window by use of
v.net.path and d.vect.

Now I want to add "Search Criteria" option with
"shortest", "fastest" and all "paths" fields.

For achieve this goal I have 2 problems:
1. I think if I don't determine the afcol and abcol,
garss find the path according to the length of the
roads, am I right? if it's correct so for finding
shortest path I should do the same as above, but there
is a problem since I want "shown path" goes regularly
through one ways, so I should use abcol=-1; and when I
use of abcol option, its necessary to use afcol option
too. And in at this time I don't know what should I
write for afcol that shows the length of the streets.
If I should know their length myself before use of
grass or ...?   

2.For fastest option I have the same problem, I don't
know what should I write for afcol in my DB, for
example If I want to use x/2 (where x is the length of
the line) for highways, how I can get the x?

in one word: How I can have the length of roads on a
map by use of GRASS?

I wish you can help me. Any suggestion will be so
appreciated.

Best Regards

Maliheh 

 

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