Writing Resources
Synthetic aperture radar SAR is a unique and well established approach for remote sensing providing high resolution digital images independent of daylight or cloud coverage Space borne SAR systems such as the current RISAT 1 RADARSAT 2 and Sentinel systems continuously yield data from extensive area of the globe with a revisit time in order of days Airborne systems on the other hand map on a more local scale but can offer lower revisit times with higher resolutions The utilizations for the acquired SAR data range from mapping of land use forest water agriculture urban to change detection based on time series monitoring of sea ice marine surveillance traffic monitoring soil moisture and biomass estimation and quick response mappings to support humanitarian aid in crisis situations A SAR system is not simply a tool for remote feature detection but it is also a measurement instrument to record reflectivity As for any other measurement instrument system calibration is hence necessary to ensure that different SAR acquisitions are comparable to each other Calibration in SAR is a cornerstone for scientific applications as well as for verifiably reliable products for a growing commercial market The SAR calibration activities are usually split into geometric and radiometric calibration In geometric calibration the SAR image coordinate system is compared with a reference coordinate system and corrections are determined and applied to ensure that SAR images are geo located with respect to a known coordinate system
