# SAR backscatter - change detection
*analysis . methodologies*

Detects land-cover or structural change by comparing backscatter intensity across dates; good for flood mapping, deforestation alerts, and disaster damage assessment.

## Specifications
- **family**: Change detection
- **requirements envelope**: {"kind":"temporal","cadence_max_days":12,"time_series_length_min":2,"cloud_tolerance_class":"immune"}
- **entity type**: methodology
- **last verified date**: 2026-05-22
- **verified by**: sw
- **claim status**: unclaimed
- **subtype**: analysis
- **attributes**: {"family":"Change detection","summary":"Detects land-cover or structural change by comparing backscatter intensity across dates; good for flood mapping, deforestation alerts, and disaster damage assessment.","requirements_envelope":"{\"kind\":\"temporal\",\"cadence_max_days\":12,\"time_series_length_min\":2,\"cloud_tolerance_class\":\"immune\"}","kind":"analysis"}

## Editorial
Single- or dual-pol intensity ratio or log-difference between acquisitions. Cloud-independent; operates day and night. The primary method for rapid flood extent mapping -- InSAR coherence is a complement, not a replacement. [Wikipedia: Synthetic-aperture radar](https://en.wikipedia.org/wiki/Synthetic-aperture_radar)

## Sources
- [wikipedia] | Wikipedia: Synthetic-aperture radar | https://en.wikipedia.org/wiki/Synthetic-aperture_radar | tier=community | accessed=2026-05-22

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Source: https://eo-atlas.org/methodologies/sar-backscatter-change-detection
Maintainer: SpectraWorks B.V. (CC-BY 4.0)