Geoid heights and tiled model

[Dieter]

In Metashape 1.74, when I work with a custom fixed height geoid and then export a tiled model and don't change the coordinate system, the output is ellipsoidal heights.

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Dieter

[Dieter]

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[Alexey Pasumansky]

Hello Dieter,

Current version of Agisoft Viewer doesn't support coordinate system selection (including compound coordinate systems), so it shows height above ellipsoid.

At the same time TLS model stores the geocentric altitude data without any relation to the geoid model used in Metashape project.

[Dieter]

Thanks for the answer.

However, this does not help me, because our customers also want the correct height (geoid) in the tiled model. Is there a workaround?



Just by the way: Why is the choice of a coordinate system offered when I export the tiled model if this selection is not taken into account anyway?


Dieter

[Medive]

I've been experiencing the exact same issue for a while now: in Metashape, the correct heights are displayed in TLS, but they are no longer accurate once the model is exported. It would be a huge help if this could be fixed

[pima]

Didn't actually noticed that. I agree it should be clear when it comes to export to TLS (a warning would help just not to waste time checking or miss that when it goes to customer).

From my experience there are a lot of conversion problems regarding coordinate systems with custom geoid in a lot of GIS software. Sometimes to avoid such problems in 3rd party software I switch Agisoft project definition from CS with geoid height to standard CS without geoid (agisoft assumes elipsoidal by default - this can be done just before exporting) with no CS height conversion/recalculation. So the CS definition (in agisoft and in exports) will say this is ellipsoidal height, but the actual height value will be geoid height. It is always better to check the result, but with small scale project and some GCP's potencial height errors that come from this "fraud" are not noticable in the products.

So use Geoid coordinates, but you can deceive agisoft that this is ellipsoid height he should use

Not a full solution but it can get the work done.

[Medive]

I am not sure, the solution is not really optimal. I also don't understand why the export, which is accompanied by a dialogue window, is not transferred in the correct height format.

I would be happy to pass on the TLS file to our site managers and project participants, who can in turn use the data for orientation, but the ellipsoidal heights alone prevent a good workflow at this point.

Alexey, where is the difficulty in including the transformed data, which are also completely correct in Metashape, in the export in order to have the same heights in the viewer? Are there any plans to implement this function..?

[Diogo]

On our projects we've been able to showcase them on the Viewer by still having the right coordinates.

In order to do so, we've exported them in the same crs including geoid. It is important that when you want to open it on the viewer, that the geoid tiff file can also be found in the Viewer geoids folder (on windows

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C:\Program Files\Agisoft\Viewer\geoids). Any export to the ellipsoidal crs will perform a transformation and the height coordinates will be wrong.

[Paulo]

I think you mean  in the geoids folder of Metashape installation directory, no?

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C:\Program Files\Agisoft\Metashape Pro\geoids
Unless you have Viewer installed as a stand-alone program without Merashape?