Hi Adam, thank you for letting us know about your projects on Pix4D Cloud.
I do not have any reason to believe that the department that previously owned your drone made any meaningful changes to your camera that would affect your project’s results.
Thank you for confirming that you used your RTK Trimble rover to collect your ground control points.
Each copy of Pix4D Desktop includes a database of camera models that Pix4D manages on an ongoing basis. The internal camera model database contains a single camera record for each camera model. Knowing that no two cameras are identical, each record in the internal camera model database is an approximation of all units of that camera model.
Pix4D’s image processing engine takes the Initial Camera Model as an input and then solves for the Optimized Camera Model each time you process a project for two reasons:
A. We do not know your camera’s internal geometries accurately enough based on the information that is available in the images’ metadata
B. Your camera’s internals can change enough over time that we do not want to automatically apply internal geometries that you solved for previously as input in another project.
Pix4D Desktop automatically applies 3.61 mm as your camera’s initial focal length because we found that it was more representative of a typical Phantom 3 Professional camera than 4 mm, which the images’ metadata and technical specifications documentation references. However, not all cameras are identical, so it is possible that your camera’s internals deviate by more than 5% from the camera model in Pix4D’s internal camera model database.
You may have noticed that Pix4D’s image processing engine arrived at 4.1 mm for your camera’s optimized focal length in your latest iteration of East Flight, which is closer to what DJI’s technical specification mentions. However, we must find a balance between the optimized values that Pix4D’s image processing engine solves for your camera’s internals and your ground control points so we cannot solely on the percent difference between your camera’s initial and optimized internal parameters to determine the quality of your project.
- I have reason to believe that excessive amounts of linear rolling shutter distortion in your images are the primary source of error in your latest reconstructions. Tests we conducted with your _East Flight _project yielded significantly better results when Pix4D’s image processing engine optimized for linear rolling shutter distortion. Please verify that you acquire similar results by enabling Linear Rolling Shutter Optimization and processing Step 1 again.
You may receive a warning in the Quality Check table highlighting that there is a significant difference between the project’s Initial and Optimized Internal Camera Model Parameters, but you can definitively verify that your results are accurate by incorporating a set of checkpoints before processing Step 2 and Step 3.
- For future projects, you can estimate whether your proposed mission is susceptible to significant amounts of linear rolling shutter distortion with Pix4D’s basic Vertical pixel displacement calculator. For your reference, we have estimated that DJI’s Phantom 3 Professional camera has a rolling shutter readout time of approximately 33 milliseconds.
Do not hesitate to let me know if you have any questions.