[gdal-dev] UTM local correction for height and distance-to-reference-meridian ?

[Thomas Knudsen]

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 at 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 at lists.osgeo.org
> https://lists.osgeo.org/mailman/listinfo/gdal-dev
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/gdal-dev/attachments/20250121/623136ed/attachment.htm>