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

[image93]

Dear all, dear Moritz,

thank you again for your last usefull messages. Regarding my driving
isochrone works. Last time (December 2014), when i executed the v.isochrones
process, an error message appeared due to running of memory. 

For remind, i 'm working on windows 7 with grass 7.0. The vector network
comes from OSM data ('roads cover). This is a big road network (490 lines
objects!!) with of course the usefull field for speed profile. My area of
interest is componed by the two french admnistrative regions (Ile de France
and Picardie). 
I have only one starting point. The projection is lambert 93. 

So i have just tried a new test. I changed the resolution (nsres : 100/
ewres :99.9) just  to ensure, for the time being, that the process works
well. But i have a new error message which would seem to have no link with
memory problem this time. I paste below the  error message : 


----------------------------------------------------------------------------
(Wed Feb 25 22:46:55 2015)                                                      
v.isochrones --overwrite map=roads_merge_idf_picardie_L93 at dataset layer=1
speed_column=speed_prof start_points=MANUTAN_starting_points_L93 at dataset
isochrones=polygons timemap=raster time_steps=15,30,45 offroad_speed=0
Reading features...
Writing raster map...
Converted points/lines: 489204 of 489204
v.to.rast terminé.
Traceback (most recent call last):
  File "C:\Users\laurent\AppData\Roaming\GRASS7\addons/scrip
ts/v.isochrones.py", line 211, in <module>
    main()
  File "C:\Users\laurent\AppData\Roaming\GRASS7\addons/scrip
ts/v.isochrones.py", line 158, in main
    null_value = resolution / (float(offroad_speed) * 1000 /
3600)
ZeroDivisionError: float division by zero
(Wed Feb 25 22:52:36 2015) La commande s'est terminée (5 min 41 sec)
------------------------------------------------------------------------------------------------------------------------

Moreover, i paste you below a SS representing map (road network and starting
point (red colour)) and also the current settings of my Grass region. 

<http://osgeo-org.1560.x6.nabble.com/file/n5190120/SS_v.jpg> 



I'm realy sorry to disturb you. But isochrony maps is really important my my
project. 

Thank you very much.





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