Hi,
Yes I think that is correct and I suggest you try this first before attempting
to handle more complicated or restricted intersections.
Sometimes in the source data for roads, for example, the reason two lines
representing paths do not intersect is because they do not, i.e. there is no
way for road traffic to change from one road to another. In England many roads
cross over each other where there is limited or no way for road traffic to
change road. Directional graphs of some sort are needed to represent
intersections where traffic may be allowed to flow only in certain ways.
HTH
Andy
http://www.geog.leeds.ac.uk/people/a.turner/
From: Harshad S [mailto:[email protected]]
Sent: 07 October 2011 09:53
To: Nicolas Malleson
Cc: [email protected]
Subject: Re: [Geotools-gt2-users] Reg AStarShortestPathFinder Class in Geotools
Hi,
So as per your reply, the generator won't take care of line intersections at
points which lie on the line excluding the end-points. This might well be the
reason for my graph being too disconnected as almost every choice of source and
dest nodes gives a disconnected path between them,
I did another check on the intersections between the line features in my
shapefile. When I manually searched the common points between any two lines
using linear search, there came out to be many such points. But, when I used
the 'intersects' function of the MultiLineString feature, there were just 3
common points. So, this means I need to split the lines at intersection points
to make my ShortestPathFinder function run correctly. Am I thinking correctly?
Please help.
Thank You.
Harshad Shrikhande
Researcher R&D
TCS Innovations Infra Lab, Chennai
Tata Consultancy Services
Cell:- 7200605821
Mailto: [email protected]
Website: http://www.tcs.com
____________________________________________
Experience certainty. IT Services
Business Solutions
Outsourcing
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-----Nick Malleson wrote: -----
To: [email protected]
From: Nick Malleson <[email protected]>
Date: 10/05/2011 01:02PM
Subject: Re: [Geotools-gt2-users] Reg AStarShortestPathFinder Class in Geotools
Hi Harshad,
My experience with the generator is that it only takes care of intersections
if the two lines that meet actually end at the intersection point. E.g. if
you have line objects that cross but don't break then the generator won't
know that they should be linked in the graph.
In my work I had to pre-process a road network so that each line is broken
at intersection points. There's a tool to do this in ArcMap (I can't
remember the name but could find it out if you want) or it is fairly
straightforward using geotools - see the splitLinesAtIntersections()
function around line 240 here:
http://geocrimedata.svn.sourceforge.net/viewvc/geocrimedata/SpatialAnalysis/src/main/java/uk/ac/leeds/ccg/spatialanalysis/spacesyntax/SpaceSyntax.java?revision=9&view=markup
Nick
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