Isodistance 100m from layer (QGIS)

openrouteservice
1

Hi,

when I use, in the QGIS Plugin, the tool “isochrone from layer” with distance 100 m, the result is sometimes wrong. When I mesure the distance between a point and the boundary of the polygon result, there may be a distance of 400 m or more.

On the service “isochrone” online, there is not the possibility to have isochrone less than 1 km. Is it the reason for the wrong result in QGIS Plugin ?

Is there a solution to obtain reliable isochrones less than 1 km ?
I have to cut my polygon result with a buffer around my point of origin, but it’s not really conclusive.

Thanks,
Best regards.

2

Hey,

when stating

what point do you mean? The origin of the polygon, i.e. the point that was used for the request?

In that case, could you share an example of where this goes wrong?
Ideally with a screenshot of your parameters, the results and possibly the actual request being sent (taken from the Log Messages-panel ORS Tools).

Yes, currently calculating isochrones with a range of less than 1 km distance is not possible in our maps client.
If this is something you’d like to see, please open an issue.

Thanks a lot

3

Hello,

Yes I mean the distance between the point that was used for the request and the furtherst border of the polygon.

For example the point 41 in this picture.

image
image511×540 63.4 KB

When I launch only isochrone with point, the result is the same. I launch with this parameters:

image
image1348×881 40.9 KB

There is no log in the panel. In the journal, when I launch the script :slight_smile: Version de QGIS : 3.22.8-Białowieża
Révision du code : 8d5e9761df
Version de Qt : 5.15.3
Version de Python : 3.9.5
Version de GDAL : 3.5.0
Version de GEOS : 3.10.3-CAPI-1.16.1
Version de Proj : Rel. 9.0.1, June 15th, 2022
Version de PDAL : 2.3.0 (git-version: 988ee3)
Algorithme commencé à: 2023-03-23T13:48:38
Démarrage de l’algorithme ‘Isochrones from point’…
Paramètres en entrée:
{ ‘INPUT_AVOID_BORDERS’ : None, ‘INPUT_AVOID_COUNTRIES’ : ‘’, ‘INPUT_AVOID_FEATURES’ : , ‘INPUT_AVOID_POLYGONS’ : None, ‘INPUT_METRIC’ : 1, ‘INPUT_POINT’ : ‘819671.105436,6525902.102528 [EPSG:2154]’, ‘INPUT_PROFILE’ : 0, ‘INPUT_PROVIDER’ : 0, ‘INPUT_RANGES’ : ‘100’, ‘OUTPUT’ : ‘TEMPORARY_OUTPUT’ }

Execution completed in 0.31 secondes
Résultats :
{‘OUTPUT’: ‘Isochrones_a274f850_3dd6_4ca7_b27b_eae49a6c4d96’}

Chargement des couches de résultat
Algorithme ‘Isochrones from point’ terminé

Thanks.

4

Hey,

thanks for the info.
This is a known issue with the algorithm used to calculate isochrones, and a rather specific edge-case only happening on rather long roads without any intersections.

Best regards

5

Thanks,

Sorry for the new issue, I haven’t see the previous.

Best regards.

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