Hi Don:
The GRASS GIS Module v.net.path will compute shortest path distances
between points
associated with a vector line dataset. The short story here is that
GRASS is a separate
open-source software package that integrates very closely with R (e.g,
spatial data move
transparently between the two systems)
You might check out the GIS links on the attached page to get a
bird's-eye view of GRASS:
http://nceas.ucsb.edu/scicomp/SoftwareLinks.html
You would have to be creative in your use of coordinate systems, but you
could solve this
problem using GRASS GIS.
Regards,
Rick Reeves
Don MacQueen wrote:
This question is basically off topic, since it isn't truly an R
question, though it is certainly related to r-sig-geo. I ask here in
the hopes that someone can suggest a direction for me to look.
I have a what is essentially a floor plan of a building (lines
representing walls, breaks in the lines representing doors, and so
on). I would like to have an algorithm that can calculate the
shortest distance between any two points (actually, large numbers of
pairs of points) that does not intersect any line (pass through any
wall).
My real dream is to use these distances instead of Euclidean
distances as input to a gaussian random fields algorithm such as
those in the RandomFields package.
I've done some web-searching for libraries of geometric algorithms
that might include this task, and have come across references to
Dystra's algorithm, and some mention of line of sight calculations,
as well as some algorithms for robotics (how the robot finds a path
from here to there, passing around obstacles represented as
polygons). So I have some leads.
None the less, I'd really appreciate any suggestions from the folks
here on R-sig-geo.
Thanks
-Don
begin:vcard
fn:Rick Reeves
n:Reeves;Rick
org:UC Santa Barbara;National Center For Ecological Analysis and Synthesis
adr:Suite 300;;735 State Street;Santa Barbara;CA;93101;USA
email;internet:[EMAIL PROTECTED]
title:Rick Reeves, Scientific Programmer/Analyst
tel;work:805 892 2533
url:http://www.nceas.ucsb.edu
version:2.1
end:vcard
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