# Network distance computations using GRASS

I'm an ArcGIS user who's interested in learning to use GRASS. Can anyone point out resources that will help me in learning how to obtain network distances between (1) residential locations (points) and (2) service locations (points also)? While I do wish to obtain the shortest paths, I need multiple paths between each residential location and a given number of services (say, the shortest paths to the 5 closest stores for each residential locations).

Help and suggestions will be much appreciated.

MP

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You can start with this GRASS tutorial on network analysis.

The aim of the exercise is to set up a GIS network to support the fire brigade interventions in the area of North Carolina. Here follows the steps of this process and the tools used:

• set up of network analysis: geometry and the appropriate database tables will be connected (v.net);
• search for the shortest path between fire stations and the road network in order to prepare a displacement map. Computation of the shortest path between some fire stations (v.net.path);
• zone the area according to the distance from fire stations to create a map of forecasted intervention time (v.net.iso);
• allocate across the network each fire station to a competence area according to the distance from the roads (v.net.alloc);
• find the shortest subnetwork linking all the fire stations in order to connect them with a high speed cable running along the streets. (v.net.steiner);
• find the shortest path connecting all the fire stations in order to optimise the route of suppliers and inspectors (v.net.salesman).
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I think that for your purpose v.net.iso is the best option. Analyze your system with services as input you can draw a map with equal-distance/cost lines in relation to each commercial location. Those residential locations that are within the cheapest/closest line to each service can count to be in its 5 locations. However it won't give you the actual path from each location to it's closest service, but will give you the "service zone" of each commercial point.

To get the closest path between a set of points to another set I recommend you to use v.net.distance. Hope I can provide more guidance on this process soon, for I'm trying to figure it out my self as well.

Dor

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I'm in a similar boat as you and this site has been more than helpful:

http://www.ing.unitn.it/~grass/docs/tutorial_64_en/htdocs/esercitazione/network_analysis/index.html

It goes through the various v.net tools in GRASS - I'm not a coder or anything, but I've become pretty familiar with GRASS over the past few months with the help of this site.

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