Reprojection Error
Definition
The distance in pixels between where the photogrammetry software predicts a feature point should appear in each photograph (based on its estimated 3D position) and where it actually appears. Low reprojection error (under 1 pixel) indicates a well-calibrated, accurate model.
- Domain
- Close-range photogrammetry
- Measured in
- Pixels
- Good threshold
- Under 1 pixel
- Indicates
- Model calibration accuracy
Common questions
What causes a high reprojection error in a photogrammetry model?+
Common causes include poor image overlap, motion blur, insufficient or poorly distributed control points, or lens distortion that was not properly modelled during calibration.
Does a low reprojection error guarantee the 3D model is forensically accurate?+
Not entirely, it confirms internal geometric consistency of the photo set, but overall accuracy also depends on the scale reference used to tie the model to real-world measurements.
Related terms
- Dense Point Cloud
- A set of millions of three-dimensional coordinate points, each with an RGB colour derived from the photographs, that together represent the surface...
- Ground Control Point (GCP)
- A physical marker in the scene whose three-dimensional coordinates have been measured independently by total station or GPS. Assigning those coordinates to...
- Orthophoto
- A geometrically corrected aerial or close-range photograph from which the distortions caused by camera tilt and terrain relief have been removed, so...
- Structure-from-Motion (SfM)
- A photogrammetric technique in which overlapping images from a drone or camera, processed by software, generate a three-dimensional point cloud and textured...
- Terrestrial Laser Scanning (TLS)
- A ground-based 3D LIDAR survey instrument that captures millions of range measurements per scan to produce a millimetre-accurate point cloud of the...