Temporal Change Detection
Definition
The comparison of multi-date images of the same area to identify pixels or features that have changed between acquisition dates. A disturbed grave site typically shows the strongest spectral anomaly in a scene acquired shortly after disturbance and compared to a pre-event baseline.
- Input
- Multi-date images of the same area
- Output
- Map of changed pixels or features between dates
- Peak signal timing
- Shortly after ground disturbance
- Field
- Remote sensing, aerial and UAV forensics
Common questions
What can cause a false change signal?+
Seasonal vegetation growth, soil moisture shifts after rain, sensor angle differences between acquisitions and shadow changes from a different sun position can all mimic a disturbance and must be ruled out before a change is attributed to a grave.
Does the anomaly fade over time?+
Yes. As vegetation recovers and the soil surface settles, the spectral contrast between the disturbed and undisturbed ground weakens, so a comparison run months after the event is less reliable than one taken soon after.
Related terms
- Ground Sampling Distance (GSD)
- The dimension on the ground represented by one pixel in an image. A 10 m GSD means each pixel covers a 10...
- 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...
- NDWI
- Normalised Difference Water Index. Computed from green and near-infrared or shortwave-infrared bands. Sensitive to water content in vegetation canopy and surface soil....
- Synthetic Aperture Radar (SAR)
- An active microwave sensor that generates its own energy pulse and measures the return from the surface. Cloud-penetrating and day/night capable. Backscatter...
- Thermal Infrared (TIR)
- Sensor bands measuring emitted heat radiation (approximately 8-14 micrometres). Decomposing organic matter generates heat; soil with high moisture retains heat longer than...