Re: [GRASS-user] Re: Drivetime Isochrones
On Sat, Jun 25, 2011 at 8:02 PM, RKiTect evan.apos...@gmail.com wrote: i think i have figured out where my problem lies. It is in the centre node costs... from the manual is says right at the top that centre node must be opened (costs = 0). however i have not defined costs for the centre node at any point... could this be the issue? how do i go about defining costs for the centre node? Defining costs or a cost column for nodes is not needed. If no cost column is given, a cost value of 0 (zero) is used for nodes, which is most of the time ok. It would help a lot if you could post the commands and the output, then it is much easier to figure out what goes wrong. You can cut and paste the output from the GUI output window. The command can be copied by clicking on the copy button. Markus M ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
[GRASS-user] Re: Drivetime Isochrones
i think i have figured out where my problem lies. It is in the centre node costs... from the manual is says right at the top that centre node must be opened (costs = 0). however i have not defined costs for the centre node at any point... could this be the issue? how do i go about defining costs for the centre node? -- View this message in context: http://osgeo-org.1803224.n2.nabble.com/Drivetime-Isochrones-tp6479604p6515373.html Sent from the Grass - Users mailing list archive at Nabble.com. ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] Re: Drivetime Isochrones
[You seem to have gotten beyond some of your troubles, but just for the record, some answers.] On 20/06/11 05:50, RKiTect wrote: Thanks for your help... unfortunately i am using the GUI and i must have an input for the 'nodes' section. Which module are you speaking about ? Neither v.net nor v.net.iso have a 'nodes' parameter. my centre layer doesn't show up for inputting into this... so i think my point file requires some sort of pre-processing, but not sure... You have to connect your points to the streets using v.net. By default this will add the points as nodes to the street network and these nodes will have category values in layer 2. v.net.iso will by default look for these category values in layer 2, so you normally don't have to worry about the layers. if you try running the gui tool you will see what i mean... inputs required for arcs and nodes, but a standard grass pointfile does not show up in nodes dropdown box... What do you mean by standard grass pointfile ? Your points have to be a vector layer. So, if you have them as an ascii file in the classic grass point format, you have to import it with v.in.ascii first. Moritz ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
[GRASS-user] Re: Drivetime Isochrones
Thanks for your help... unfortunately i am using the GUI and i must have an input for the 'nodes' section. my centre layer doesn't show up for inputting into this... so i think my point file requires some sort of pre-processing, but not sure... if you try running the gui tool you will see what i mean... inputs required for arcs and nodes, but a standard grass pointfile does not show up in nodes dropdown box... -- View this message in context: http://osgeo-org.1803224.n2.nabble.com/Drivetime-Isochrones-tp6479604p6494579.html Sent from the Grass - Users mailing list archive at Nabble.com. ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] Re: Drivetime Isochrones
On 16/06/11 19:54, RKiTect wrote: **UPDATE** Ok, so i have figured out one part of the problem. Perhaps somone can provide some further guideance? I have used the v.net function on my arc shapefile, using the nodes operation to create another shapefile with just the nodes of the network. I can then input into the v.net.iso tool both of these files (the arc and nodes layers respectivlely). up to this point i am stuck, becuae i can't figure out how to specifiy the centre points for the isoline calculations... i am thinkning i need to modify the attribute table of my nodes layer, but not sure how this should be done... does anyone have any experience in using v.net.iso in GUI format, that could help me? Any input is much appreciated. 1) Connect centre points to roads: v.net input=roads points=centre_point output=roads_with_point operation=connect threshold=DistanceBetweenPointAndNearestLineInNetwork 2) Create isoline vector v.net.iso input=roads_with_point output=isolines ccats=1-999 costs=TheDistanceThresholds Please be aware that this module does not create a surface, but affects each line of the network to one of the classes defined by your cost thresholds. You could possible use interpolation afterwards to create a surface from these lines. Moritz ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
[GRASS-user] Re: Drivetime Isochrones
**UPDATE** Ok, so i have figured out one part of the problem. Perhaps somone can provide some further guideance? I have used the v.net function on my arc shapefile, using the nodes operation to create another shapefile with just the nodes of the network. I can then input into the v.net.iso tool both of these files (the arc and nodes layers respectivlely). up to this point i am stuck, becuae i can't figure out how to specifiy the centre points for the isoline calculations... i am thinkning i need to modify the attribute table of my nodes layer, but not sure how this should be done... does anyone have any experience in using v.net.iso in GUI format, that could help me? Any input is much appreciated. -- View this message in context: http://osgeo-org.1803224.n2.nabble.com/Drivetime-Isochrones-tp6479604p6484114.html Sent from the Grass - Users mailing list archive at Nabble.com. ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
