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Quality Checks & Statistics

In photogrammetry reports, messages are provided in case that Ground Control Points (GCP) error does not fall within acceptable tolerances. Picture Positions and Camera Calibration quality is assessed as well. The criteria for each are detailed hereafter.


1. Ground Control Points

Error on GCP is compared to Ground Sampling Distance (GSD) ; error in X and Y shall not exceed 2xGSD ;  in Z it shall not exceed 3xGSD.


OKGCPs are used and the GCPs error is less than the average GSD
WARNINGGCPs are used and the GCPs error is less than 2 times the average GSD or no GCPs are used
FAILUREGCPs are used and the GCPs error is more than 2 times the average GSD.



2. Picture Positions

OKKeypoints Image Scale > 1/4: More than 10,000 keypoints have been extracted per image or Keypoints Image Scale ≤ 1/4: More than 1,000 keypoints have been extracted per image
WARNINGKeypoints Image Scale > 1/4: Between 500 and 10,000 keypoints have been extracted per image or Keypoints Image Scale ≤ 1/4: Between 200 and 1,000 keypoints have been extracted per image
FAILUREKeypoints Image Scale > 1/4: Less than 500 keypoints have been extracted per image or Keypoints Image Scale ≤ 1/4: Less than 200 keypoints have been extracted per image



3. Camera Calibration

OKPerspective lens: The percentage of difference between initial and optimized focal length is less than 5%
WARNINGPerspective lens: The percentage of difference between initial and optimized focal length is between 5% and 20%
FAILUREPerspective lens: The percentage of difference between initial and optimized focal length is more than 20%

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