[GRASS-user] grass : how to do Isochrone maps?

[Moritz Lennert]

On 09/12/14 17:37, image93 wrote:
> Hello,
>
> Thank you very much. The v.isochrones seems to require in input a vector
> network (roads) with a speed attributes column. I have just checked my
> openstreetmap roads vector layer. And this column is not fully completed,
> data are lacking for many routes. How can I do? According to you, before
> applying v.isochrones, should I do anything on the input data (editing about
> attributes or/and geometry/topology) ?

v.isochrones does not require a topologically clean network. If possible 
errors (e.g. non-closures) are below resolution size, they should not 
even make any difference.

As mentioned privately, I actually haven't tested the module with 
missing speed attribute data, so I don't know the consequences and don't 
have time currently to look into that.

Moritz