Quick Answer: SAR (Synthetic Aperture Radar) works through clouds and at night, ideal for flood mapping and disaster response. Optical imagery provides natural colors and vegetation indices (NDVI), best for agriculture and land cover analysis. Use SAR when weather is poor; use optical for detailed visual analysis.
SAR vs Optical Satellite Imagery
Understanding the differences between SAR (radar) and optical satellite imagery is essential for choosing the right data for your analysis. This guide compares Sentinel-1 SAR and Sentinel-2 optical imagery.
SAR (Radar)
Sentinel-1
Best for: Flood mapping, disaster response, ship detection, deformation monitoring, all-weather monitoring
Optical
Sentinel-2
Best for: Agriculture, vegetation health, land cover, urban planning, water quality, visual interpretation
Feature Comparison
| Feature | SAR | Optical |
|---|---|---|
| Works through clouds | ||
| Day and night operation | ||
| Natural color imagery | ||
| Vegetation indices (NDVI) | ||
| Flood detection | ||
| Ship detection | ||
| Urban mapping | ||
| Biomass estimation | ||
| Surface deformation (InSAR) | ||
| Water quality analysis |
When to Use Each Type
Flood Mapping
SAR RecommendedSAR works through clouds that often accompany storms. Water appears dark in SAR imagery, making flood extent clearly visible.
Vegetation Health (NDVI)
Optical RecommendedOptical sensors capture red and near-infrared bands needed to calculate NDVI and other vegetation indices.
Ship Detection
SAR RecommendedMetal ships appear as bright points in SAR imagery. Works at night and through clouds for maritime surveillance.
Land Cover Classification
Optical RecommendedMultiple spectral bands allow accurate classification of vegetation types, urban areas, and water bodies.
Disaster Response
SAR RecommendedImmediate imagery availability regardless of weather or time of day is critical for emergency response.
Agriculture Monitoring
Use BothOptical for crop health (NDVI), SAR for soil moisture and crop structure. Best results combine both.
Technical Specifications
Sentinel-1 (SAR)
- Frequency: C-band (5.405 GHz)
- Wavelength: 5.6 cm
- Resolution: 10-20 meters
- Revisit: 6 days
- Polarization: VV, VH
- Archive: 2014-present
Sentinel-2 (Optical)
- Bands: 13 spectral bands
- Resolution: 10m (visible), 20m (red-edge)
- Revisit: 5 days
- Swath: 290 km
- Product: Level-2A (atmospherically corrected)
- Archive: 2015-present
Try Both in Off-Nadir Delta
Access Sentinel-1 SAR and Sentinel-2 optical imagery for the same location. Layer both sensor types and toggle between them to understand which works best for your needs.