Optical and SAR sensors are among the most commonly used geospatial data sources. The choice between them depends on various factors, including the AOI, the intended use case, and the technical workflow.
Optical sensors deliver detailed imagery using visible and infrared light but can be restricted by weather and lighting. In contrast, SAR sensors capture data in all conditions, day or night, making it ideal for areas with frequent cloud coverage or for disaster monitoring.
Optical
- Captured with passive sensors that only receive radiation.
- Depends on lighting conditions and are almost always captured during the day.
SAR
- Captured with active sensors that emit and receive radiation.
- Doesn’t depend on lighting conditions, enabling capture during day and night.
- Uses different polarizations to collect various types of surface information.
Optical
- Represents visible and infrared light.
- Is affected by atmospheric conditions like clouds, fog, and smoke.
SAR
- Represents microwave radar waves.
- Isn’t affected by atmospheric conditions like clouds, fog, and smoke.
- Can see through vegetation and shallow ground at higher wavelengths.
Optical
- Has a uniform spatial resolution.
- Can be post-processed, using pansharpening or upsampling, to improve spatial resolution.
SAR
- Has varying resolution in the azimuth and range directions.
- Can be post-processed using multi-looking to reduce noise, but this comes at the expense of effective resolution.
Optical
- Provides data in raster formats.
- Allows processing and interpretation with most GIS software.
- Can be overlaid and mosaicked with other optical imagery.
SAR
- Provides data in complex, detected, and geocoded processing levels.
- Needs specialized processing techniques to generate meaningful insights.
Optical
- Supports visual analysis with detection algorithms.
- Enables urban and agricultural analysis.
- Can be used to extract spectral indexes.
SAR
- Supports monitoring areas with frequent cloud coverage, like tropical or polar regions.
- Enables biomass and vegetation structural analysis.
- Can be used for SAR interferometry or InSAR to assess ground subsidence and infrastructure stability.
SAR and optical products are complementary and can be combined to provide more comprehensive insights. Apply combinations of the two types of products for the following use cases:
- Disaster damage assessment
- Forest monitoring and carbon assessment
- Soil and crop monitoring