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Processing Sentinel 1 SLCs
The content of the tutorial is produced by postdoc scholars and faculty members at EOS. For permission to use the content of the material for your work, please contact our researchers.
Curators: Alok Bhardwaj, Shi Tong Chin, Nina Lin
The Sentinel-1 SLC (S1 SLC) dataset contains the Synthetic Aperture Radar (SAR) data obtained by the sensor Sentinel-1 operating in the microwave C-Band wavelength. The SAR sensors are installed on a two-satellite (Sentinel-1A and Sentinel-1B) constellation orbiting the Earth. The S1 SLC data are a Level-1 data product, which is obtained from Level-0 raw data after a series of processing steps including internal calibration, Doppler centroid estimation and single look complex focusing (range and azimuth processing). The Level-1 SLC product consists of geo-referenced focused SAR data in slant-range geometry. The Level-1 SLC product also preserves the radar amplitude and phase information in all-weather, day or night conditions. For more information on the SLC product please refer to the Sentinel web-page on European Space Agency (ESA) (https://sentinel.esa.int/web/sentinel/missions/sentinel-1/data-products).
A SLC contains SAR amplitude and phase information. Amplitude refers to the strength of the signal backscattered from the ground, whereas phase carries distance information between the satellite and the ground. For a co-registered SLC pair, the difference in the phase information can be exploited to measure the changes in the topography that occurred between the acquisition of the SLCs in the pair. This phase difference, or interferometric phase, forms the interferogram, usually presented in the form of 2-pi cycles (or fringes). The main steps for generating an interferogram includes co-registration of SLCs and topography removal. For obtaining the continuous ground displacement field, phase unwrapping and phase to displacement conversion are applied. In this tutorial, we are demonstrating how to generate an interferogram from a given SLC pair. Processing of SLCs can be done via GMTSAR which is an open source interferometric SAR (InSAR) processing software based on Generic Mapping Tools (GMT). The following is a list of online resources to learn more about GMTSAR: