Geoid Height in pix4DMapper vs. Selecting the geoid in pix4Dsurvey

PIX4Dsurvey
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Until recently the orthometric height obtained in Survey came from Mapper where it was defined under project initialization (geoid height above ellipsoid). Thus I believed that the LAS-file in …2_densification\point_cloud held points with orthometric height.

In the latest version of Survey the user have got the option to choose between “Ellipsoidal height over the WGS 84 ellipsoid” and “Vertical coordinate reference system” and a corresponding geoid.

This indicates that LAS-file always holds points with ellipsoidal height. Is that correct ?

One remark or note on a possible error:

Altough you input a geoid height above ellipsoid in pix4DMapper before processing AND you accept Ellipsoidal height over the WGS 84 ellipsoid as vertical coordinate referance system in pix4DSurvey, you WILL see orthometric Height at the bottom of the screen.

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Holden Greene

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2 minutes ago

Hi Tibor,

Thank you for reaching out. Can you clarify what orthometric height model you have been using in PIX4Dmapper?

In regards to your question, This indicates that LAS-file always holds points with ellipsoidal height. Is that correct ?

This would depend on the output CS options declared in PIX4Dmapper. If it is one of the supported global geoids EGM96, etc, then it would be orthometric. If not then it would be ellipsoidal. If you are entering a geoid height above ellipsoid then by nature it would be an ellipsoid height in the output.

*** Although you input a geoid height above ellipsoid in pix4DMapper before processing AND you accept Ellipsoidal height over the WGS 84 ellipsoid as vertical coordinate reference system in pix4DSurvey, you WILL see orthometric Height at the bottom of the screen.***

The units shown at the bottom of the screen in PIX4Dsurvey are the project CRS, not the input data CRS. So if you have an orthometric VRS defined it should transform the units to reflect your selection. If as you say you have selected ellipsoidal for both this would not be expected behavior. Can you document how you are determining this so that I can review with the developers?