[GRASS-user] Network analysis

[Giovanni Pasini]

David Dabin ha scritto:
> Dear Grass Users/Developpers,
> 
> I am studying the distribution of car accidents on a road network. In 
> order to define hotspots and hotzones (succession of hotspots on a road) 
> based on a  local density of accidents computed on the network, I use 
> the v.net.alloc function (to allocate a subnet to each accident event). 
> For the moment, the density is thus expressed per "Thiessen" segment. To 
> illustrate, Typical output is similar to
> 
> ----x---|---x-|-x--|--x----
> 
> where
>    x: is the location of one or many accidents,
>    -: is a piece of the network,
>    |: is the limit of the Thiessen segments
> 
> My density of accident is simply the number of accident divided by the 
> length of the Thiessen segment. Howerver, as you can notice from the 
> example, the Thiessen segments (|---x-|) are not symmetric relatively to 
> the accident location. I thus would like to compute the length on the 
> right and on the left of each segment. I have tried to cut the output of 
> v.net.alloc with v.edit and coordinates of accident but it do not works. 
> Do you have an idea on how to proceed and which function should I use or 
> implement?
> 
> Thanks in advance,
> David
> 
> 
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Not responding to your question...

see also v.kernel [1] > vector density map on vector network with a 1D 
kernel

[1] http://grass.itc.it/grass64/manuals/html64_user/v.kernel.html

giovanni