[GRASS-user] v.net.steiner success!

[M S]

after 3 weeks of perserverance, i am victorious!

the biggest problem i was having was with the v.clean portion to tie
together the connections with the streets.  I used GRASS 6.0.2.

1) i took buildings (points) and used v.distance to the streets (lines) to
create connectors (lines)
2) added category values to connectors, (otherwise v.patch would put them on
layer ZERO.
3) used v.patch to patch buildings, connectors, and streets together.
4) ran v.clean - this was the biggest problem.  I was expecting the
connectors to break the line where it "touches" it.  it would not break the
line.  it seems that the connectors would only snap to nearby nodes or
vertexes (cant recall if it did snap to verticies).  so i had to go through
208 points and verify that the line had a node where the connector was
meeting the road.  i used the split tool in QGIS editing the GRASS vectors
for each one.
5) ran v.clean again to snap to the manually created nodes.
6) ran v.net.steiner.

depending on how long it takes on one's machine to compute the steiner tree,
i highly recommend verifying all points manually that they are snapped to
streets.  using QGIS i was able to do this relatively quickly, by looking
for red X's that indicated no connection.

i had to strip down the streets because 28K of them and 208 buildings took 8
days till i bailed.  so i cleaned out roads that i knew it would not route
along (mostly dead ends).  after doing this, it ran with about 9K street
lines, and took about 2 days.  the biggest hangup was v.clean not breaking
lines where connectors met.  i assumed it was doing this but learned the
hard way it did not.

one solution i forsee is to use v.split in 6.1, which can add (unnecessary)
verticies every X distance.  I believe this would help the connectors find
vertex points to snap too.  if it doesnt snap to vertexes, then it may not
help.

if i can help anyone with this process feel free to ask!

Great work from the GRASS developers on this one.  A network
engineer/planner is reviewing the results and is impressed
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