If you bring the patched data (nodes/terminals and arcs) into v.digit, do you see dangling arcs (red) that might cause the network to be disconnected? Particularly at the patched nodes?
On 8/3/07, Joseph Guillaume <[EMAIL PROTECTED]> wrote: > > Hi, > > I'm trying to run a travelling salesman analysis between point features on > a road map, but it tells me that two nodes are unreachable from one another, > which is a fatal error. > > I've successfully done this exact analysis using ARC/View, but I'm trying > to find an OSS alternative that works on Debian - and it seems GRASS is the > only software currently able to do network analyses. > > I patched together two ESRI shapefile datasets, following the Grass 6.0 > v1.2 tutorial. > I tried linking the attributes to the original datasets and tried without > linking. > I tried putting the new points on both the same layer and a new layer. > I tried running every single v.clean function on both the original and > patched datasets. > I am certain that all the points are actually on the network. > I've searched all mailing lists, reference materials, and bugtracker, but > didn't find anything explicitly related to unreachable nodes. > > Assuming the error message does mean that the map I am using has segments > disconnected from the rest of the network, the questions are: > > * How do I detect them and remove them? > The node numbers given don't match the cat attribute, so I assumed they > referred to the id attribute. The two nodes referred to by id are however > connected to each other (directly) and to the main part of the network. I > suspect the node numbers therefore don't correspond to any attribute as > such, but are rather internal. In that case, how do I identify the actual > nodes/segments responsible? > > * Shouldn't the algorithm be tolerant of such errors anyway? > I checked, and none of the relevant nodes are actually within segments I > can see are disconnected, so the analysis results should be the same if the > algorithm ignored the error... Is this perhaps because of the heuristics > used to solve this NP-hard problem? Does anyone know what ArcView does > differently? > > > > Any ideas? > > Cheers, > > Joseph Guillaume > > _______________________________________________ > grassuser mailing list > [email protected] > http://grass.itc.it/mailman/listinfo/grassuser > >
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