patiam
 Core User of DJI
Flight distance : 1156358 ft
United States
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dodger_rog Posted at 6-30 19:05
We use a global adjustment from the ellipsoid height to geoid height for each project based on the surveyed GCPs. The correction is the average difference between each GCPs ellipsoid to geoid values. We typically find across the project area there is a less than 1cm variation in these values.
In my opinion, I don't think there would be an observable improvement in accuracy by adjusting each image individually.
Depends on the size of the project, and where it is. In some areas geoid height can vary by many cm over km or even 100s of m. If your project is large and you're using Pix4D, you're stuck with applying a single (global) shift, which may not maintain project tolerances in such areas.
One solution is to break the project up and use appropriate geoid separation values for each. Another is to keep the project in HAE and then shift all the outputs using a text or raster geoid model from NGS (in the US).
The better solution would be if Pix4D would allow us to simply point to a file instead of entering a single value for geoid height. I've lobbied them for such an enhancement, and I'm lobbying other users to do so as well. The squeaky wheel and all that... |
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