I’m using a Phantom 4 RTK to do topographic drone surveys on construction sites.
I have a inquiry about the best way to process a survey information in Pix4D using the OSGB 1936 British National Grid.
At the moment, I use Grid InQuest II to transform the GeoTiff coordinates from ETRS89 Geodetic to OSGB36/ British National Grid (Tn15/GM15) and add the transformation of the x, y, z to Pix4D for the input coordinate system and for output I select the OSGB 1936 for x, y coordinate system and the vertical coordinate system I select the Airy 1830 ellipsoid.
Is the Pix4D transformation from WGS84 to OSGB36 the same as the Grid InQuest II (transformation software from the Ordnance Survey)?
If you have a local grid, would you still bother to make the transformation from WGS84 to OSGB36 and then adding the ground control point to bring the survey into the local grid? Or simply just use the WGS84 for input and output but selecting the vertical coordinate system as variable and adding the ground control points?
Also, would you use ground control points if your coordinate system is OSGB1936 and not a local grid? Is it going to make a difference in accuracy for level and position between a survey with GCP and a survey without? I’m looking at different ways to speed up the process of drone surveying because at times it take the same amount of time as traditional surveying done with a GPS kit.
And lastly, if you have OSGB36 input coordinate system, and output x, y OSGB36 but Z vertical coordinate system selected as variable, how is z going to be calculated? in OSGB36 or at a random value?
Thank you all!