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Final height of the processed orthomosaic


I have the following question about the option to enter the height of the geoid with respect to the ellipsoid.

In the option of the vertical coordinate system. Knowing the height of the geoid on the ellipsoid (52.51m) of my work zone. I am working in Spain with the geodetic reference system ETR89 (which does not appear as an option in Pix4d).

I take control points (GCP) with GPS RTK (coordinates WGS84 with ellipsoidal height). The height of each point is on average 450 m.

The images of my DJI team have a height error of approximately 40 meters.

The questions is as follows.

  1. Should I enter the geoid height (52.51m) in the options of the images, GCP and Output at starting process n ° 1? I must enter it in the three options. It will correct my height automatically from the ortomosaic?
  2. The final result with respect to the height of the ortomosaic will be, for example, 450 (GCP) - 52.51 (height of the geoid on the ellipsoid) = 397.49. Is the subtraction of orthometric height = GCP ellipsoidal height - geoid height done internally in the software.

Beforehand thank you very much.

Hi Felipe,

  1. You should enter the VCS used to capture your images as your image VCS and the GCP VCS should be set to whatever was used when they were collected. If you want to get your outputs in the geoid shifted VCS then just apply the offset to your output VCS. Alternatively, you could capture your GCPs in the desired geoid and set the GCP VCS and the output VCS to arbitrary. This will have your outputs corrected to the geoid elevations that are in the desired geoid. 

  2. The correction of the output elevations for orthometric height is done automatically if the geoid is one of the supported geoids or if the height above ellipsoid value is provided.