from a practical standpoint, it looks like in your image the origin point for the isolines is central Paris, not the yellow dot to north.
By way of comparison with your image, what do results look like if you use v.net.iso? This will return lines with each ISO cost value, not a surface. It thus is a two step process to create a surface (potentially giving you more options), but it might help to isolate the cause of the problem.
So with max speed limits, you mean you updated the forward and backward cost columns, taking into account length too?
When i modify the resolution nres/ewres from 1 to "150", i have no longer
error message. But when i try a process with a resolution with a value <
150, the process is endless...According to you, the results generated at this resolution (150) would be
relevant? valid?I loaded the output vector into qgis. The results are seem incoherent. The
curves show that we can go in 15 minutes on the other side of Paris! In
reality, From my starting point we would go much further toward toward north
than south west...
I use OSM data. I edited and populated the max speed field thanks to the
value of another filed (type of road).
How to explain this incoherence? Due to v.isochrones? Due to resolution? Due
to input maxspeed values ?I am annoyed because it seems impossible to generate the results for a
better resolution than 150.
Thanks.I paste below a SS representing results.
