Glossary for Geospatial Science

SAR:  Synthetic Aperture Radar.  SAR uses a microwave instrument that sends pulsed signals at targets and processes the return signals that it receives.  The SAR sensor can function day or night and regardless of weather conditions.  SAR differs from other radar imaging processes because it synthesizes a greater antenna length than actually exists.  Signals received and recorded by the radar system as it moves along its flight path are Doppler-shifted.  By comparing the Doppler frequencies to a reference frequency, many of the returned echoes are focused on a single point effectively increasing the length of the antenna that is imaging on that point.  Very precise knowledge of the relative motion between the sensor platform and the imaged objects is required.