Crop Mark
Definition
A differential growth or colour pattern in surface vegetation caused by a sub-surface soil change, including disturbance from digging, which alters moisture retention and nutrient availability above the anomaly.
- Type
- Differential growth or colour pattern in vegetation
- Cause
- Sub-surface soil disturbance
- Mechanism
- Altered moisture retention and nutrient availability
- Field
- Aerial and satellite remote sensing
Common questions
How can a crop mark indicate a buried clandestine grave rather than just a natural soil variation?+
A disturbed burial fill typically differs in compaction, drainage, and nutrient content from the surrounding undisturbed soil, and this produces a localised, often geometric growth or colour anomaly in the vegetation above it that natural variation does not usually replicate.
Why is aerial or satellite imagery useful for spotting crop marks compared to ground-level observation?+
The scale and pattern of a crop mark is often only visible from an elevated or overhead viewpoint, and multispectral or infrared imaging can highlight vegetation stress differences that are not obvious to the naked eye at ground level.
Related terms
- 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...
- Orthomosaic
- A geometrically corrected image assembled from many overlapping photographs, with a consistent scale across its extent. UAV-derived orthomosaics can be georeferenced to...
- 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...