Level-1 Products - Sentinel-1 SAR Technical Guide - Sentinel Online
Sentinel-1 Level-1 products are the baseline products for the majority of users from which higher levels are derived. From data in each acquisition mode, the Instrument Processing Facility (IPF) generates focused Level-1 Single Look Complex (SLC) products and Level-1 Ground Range Detected (GRD) products.
SAR parameters that vary with the satellite position in orbit, such as azimuth FM rate, Doppler centroid frequency and terrain height, are periodically updated to ensure the homogeneity of the scene when processing a complete data take. Similarly, products generated from WV data can contain any number of vignettes, potentially up to an entire orbit's worth.
All Level-1 products are geo-referenced and time tagged with zero Doppler time at the centre of the swath. Geo-referencing is corrected for the azimuth bi-static bias by taking into account the pulse travel time delta between the centre of the swath and the range of each geo-referenced point.
A Level-1 product can be one of the following two types:
GRD products are further classified by resolution (Full, High or Medium). Note that FR is only available for Stripmap mode.
Rng x Azi [m]
Ring x Azi [m]
Ring x Azi
In the table above, for GRD Products, the resolution corresponds to the mid-range value at mid-orbit altitude, averaged over all swaths. For SLC SM/IW/EW products, the resolution and pixel spacing are provided from lowest to highest incidence angle. For SLC WV products, the resolution and pixel spacing are provided for beams WV1 and WV2.
For SLC products, the range coordinate is in slant range. All the other products are in ground range. For GRD IW/EW products, the equivalent number of looks corresponds to an average over all swaths.