Orthomosaic
Definition
A geometrically corrected image assembled from many overlapping photographs, with a consistent scale across its extent. UAV-derived orthomosaics can be georeferenced to sub-metre accuracy and used as legal exhibits.
- Input
- Many overlapping photographs
- Key property
- Consistent scale across the whole image
- Source platform
- UAV/drone imagery
- Achievable accuracy
- Sub-metre georeferencing
Common questions
How does an orthomosaic differ from simply stitching photographs together into a panorama?+
A panorama stitch preserves the perspective distortion of the original images, so scale varies across the frame, while an orthomosaic corrects for camera tilt, lens distortion and terrain relief so that any point on the image can be measured at a consistent scale, making it usable as a scaled map rather than just a wide picture.
Why does georeferencing accuracy matter when an orthomosaic is used as a legal exhibit?+
A court relies on the image to represent true ground positions and distances, so the georeferencing accuracy determines how confidently a measurement taken from the orthomosaic, such as distance between evidence items or a scene boundary, can be presented as reliable rather than approximate.
Related terms
- Crop Mark
- A differential growth or colour pattern in surface vegetation caused by a sub-surface soil change, including disturbance from digging, which alters moisture...
- Multi-Temporal Analysis
- Comparison of imagery acquired at different dates to detect change. A soil disturbance present in a 2009 image but absent in 2005...
- NDVI
- Normalised Difference Vegetation Index. Computed as (NIR-Red)/(NIR+Red) from multispectral imagery. Values near 1 indicate dense healthy vegetation; values near 0 indicate bare...
- SfM (Structure from Motion)
- A photogrammetric method that builds a 3D point cloud and orthomosaic from overlapping images by computing camera positions and feature matches. Standard...
- UNOSAT
- The UNODC Satellite Centre, a UN programme that provides satellite-derived analysis in support of humanitarian and legal investigations, including imagery used for...