Hi Joe, thanks for following up.
Matt sent us the Quality Reports of his two projects.
The project has 21 nadir images over a parking lot that had a few trees and cars. The Processing Options Template was correctly selected as 3D Maps and the camera model was selected from the Pix4D camera database (see the icon on the left):
The difference came from the Camera Optimization that was different in both runs of the projects (17.6% and 6.36%), see below:
We recommend to have the Camera Optimization below 5% , if the difference is larger, there could be issues in the reconstruction. Note that this is the general case for cameras from the Pix4D camera database. A few options to improve this in the projects above:
Take more images
We consider a project with less than 30 images to be very small. When there is not enough information, it can lead to different results during the calibration of the images.
Therefore, we recommend to take more images, which should improve the calibration of the cameras during step 1. Initial Processing.
(optional) Linear Rolling Shutter correction
As seen above, the project is using a DJI camera. Most DJI cameras have a linear rolling shutter on their camera, which can lead to the Rolling Shutter Effect depending on the drone speed (the faster it flies, the more probable it is that there is a Rolling Shutter Effect). A visible effect is that the reconstruction is a bit curved. This can be corrected in the software as described in this article:
All Prior option
During 1. Initial Processing, the software tries to optimize the camera model. As there were not many images it found different solutions each time. As the camera is from our camera database, the model of the camera is supposed to provide good initial parameters. Therefore, we can tell the software to “trust” these parameters and to remain close to these values for the optimized parameters.
This can be done by selecting the option “All Prior” in Process > Processing Options > 1. Initial Processing > Calibration > Internal Parameters Optimization. Then, step 1. Initial Processing should be reprocessed.