gdal_proximity.py gives wrong distance
|Reported by:||remilemoy||Owned by:||warmerdam|
Description (last modified by )
When computing distances between all points of a raster and a given pixel (the center of a city in a monocentric city model) using gdal_proximity.py, I obtained wrong distances. The error is not big, but not very small either, something like 5 or 10% (500-900m for 10km), depends on the CRS I used (I tried another one because I thought it was CRS-related) and is bigger in a North-South direction than East-West.
I saw the error when I computed the distance in another way (euclidian distance using the projected coordinates). I am confident that this euclidian distance is right because I compared it to the one given by an online national GIS system (http://www.geoportail.gouv.fr -- I was working on a French city), and the distances I measured were in good agreement (and it worked for both CRSs I tried).
So I will just stop using gdal_proximity, also because I don't really need it in this project, but I wanted to mention the error -- I hope that this is the right place to do so.
Sorry if it is actually my mistake, I am still a beginner with GIS!