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Best Process Settings for Processing 3D Building Models

Can someone please advise where to find a good tutorial for 3D building model data collection, and for best settings in Pix4D for processing 3D building models?

I’m using the Pix4Dcapture app using a double grid mission (DJI P4P v2 and Mavic 2 Pro).  Under step 1. Initial Processing > Matching, I’m a bit confused whether to select either “Aerial Grid or Corridor” or “Free-flight paths or Terrestrial” since the default processing option when selecting the 3D model processing option is “Free-flight paths or Terrestrial” yet the flight data set is captured as an “Aerial Grid” data set.     

I couldn’t find anywhere in the support knowledge base this is clearly defined, and why the default is set to “Free-flight paths or Terrestrial” other than it mentions briefly “for example, taking images around a house or a statue” as to use this for a fly around for towers or around a building in an orbit flight? Which one is the correct one to select for 3D building models?

Also should “Use Geometrically Verified Matching” be selected, since it is also not set as default?

Further,  on a data set I had generated using a double gird (Using Litchi) and with oblique camera slightly forward pointing, the data set ended up concave. I see the computed optimized camera points are raised at the perimeters a lot from where the GPS points are. Any idea why this has happened?

Any advise would be much appreciated.

Hi John,

I would recommend processing this type of projects with the 3D Maps template together with the “Aerial Grid or Corridor” as the mission was flown in a regular pattern. More information about the templates can be found in the Processing Options Default Templates article. 

If you see any symptoms in your project that are commonly due to excessive amounts of linear rolling shutter distortion in your images, e.g. your  results bending or an extreme difference between your camera’s initial and computed internal camera model parameters, etc., we recommend the following:

  • Enable the linear shutter optimization in the Image Properties Editor
  • Capture the project area again while flying slower and/or higher to reduce the amount of linear rolling shutter distortion that is present in your images. You can see how your camera and flight parameters influence the amount of linear rolling shutter distortion that is present in your images with Pix4D’s Vertical Pixel Displacement Calculator.
  • If the results are not satisfying, we recommend using the All Prior camera optimization option together with the linear rolling shutter algorithm.