If you plan to transform to a different system anyway, I would definitely prefer going to geographical coordinates, and computing the length of the geodesic between the two points.
First step in converting between a projected system and the earth centered cartesian XYZ, is using the inverse of the source system, going to geographical anyway. So the difference in computational cost between a geodesic and a 3D cartesian computation, will probably be negligible. Den tirs. 21. jan. 2025 kl. 09.18 skrev Peter Bennewitz via gdal-dev < gdal-dev@lists.osgeo.org>: > Dear all, > > it's more of an application question than a developer's , - AFAIK there's > only 'gdal-dev' ? Mea culpa if this doesn't belong here. > > To get exact distances between local points, UTM requires a correction > factor, depending on local height and distance to the UTM reference > meridian. Mainly due to UTM's 6deg steps, - as opposed to the smaller 3deg > of GK, where this correction could have been neglected. My current idea is > be to transform an area of 10km x 12km to XYZ coordinates that closely > match 'field measurable' distances between two points. > > (Pls note that this isn't LatLon<->UTM , for which there are heaps of > howto websites) > > What would be the advised way to handle this in GDAL ? Or a good keyword > to find this in the GDAL doc ? "local coordinates" maybe ? Or convert the > dataset to the older GK and just use that ? > > Any pointers much appreciated, TIA, best, > Peter > _______________________________________________ > gdal-dev mailing list > gdal-dev@lists.osgeo.org > https://lists.osgeo.org/mailman/listinfo/gdal-dev >
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