The document discusses compact polarimetry for SAR systems. It defines compact polarimetry as using one transmit polarization and two receive polarizations. This allows for larger swaths compared to full polarimetry. Calibration of a compact polarimetry system requires three reference targets and has fewer unknown parameters than a full polarimetry system. Simulations show compact polarimetry data can be accurately reconstructed from full polarimetry raw data. Analysis of biomass estimation using compact polarimetry data found errors similar to using actual full polarimetry polarization channels.