Some users will opt to provide Propeller with a camera calibration file to apply to photos before the photogrammetric process begins.
Note: These camera calibration files must be emailed to the user’s Customer Success Engineer as they cannot be accepted directly in the upload process.
Camera calibrations commonly exist in .xml format. An example of a camera calibration file can be seen below.
f – camera focal length
cx, cy – the center of camera sensor or principal point (x,y)
k values – distortions from the center of the lens (radial distortions)
p values – lens misalignments (tangential distortions)
There are 3 ways Propeller can handle camera calibrations:
Propeller can “lock” the calibration, which means the values provided in the XML file will be applied to all flights.
Propeller can choose to use the provided XML as our “starting point” when beginning the auto-calibration process on a per-flight basis.
Propeller can auto-calibrate independent of any XML file to land on an optimal value for each flight.
In our testing, Options 2 and 3 produce the best results, with no significant difference between the two. Option 1 tends to produce models with worse accuracy in most situations. Allowing the calibration values to adjust slightly from flight to flight better accounts for slight changes in the camera’s hardware due to changing climate conditions.
I still can't do it!
We wrote these articles to equip you with everything you need to get the job done on your own, but we understand that sometimes this isn't sufficient.
If you're stuck, you can connect with our support team by clicking the support button on the top right corner of your user portal.