Forest mapping and monitoring with interferometric Synthetic Aperture Radar (InSAR)

8 9 10 A Synthetic Aperture Radar (SAR) is an active sensor transmitting pulses of polarized 11 electromagnetic waves and receiving the backscattered radiation. SAR sensors at different 12 wavelengths and with different polarimetric capabilities are being used in remote sensing of 13 the Earth. The value of an analysis of backscattered energy alone is limited due to ambiguities 14 in the possible ecological factor configurations causing the signal. From two SAR images 15 taken from similar viewing positions with a short time-lag, interference between the two 16 waves can be observed. By subtracting the two phases of the signals, it is feasible to eliminate 17 the random contribution of the scatterers to the phase. The interferometric correlation and the 18 interferometric phase contain additional information on the three-dimensional structure of the 19 scattering elements in the imaged area. 20 A brief review of SAR sensors is given, followed by an outline of the physical foundations of 21 SAR interferometry and the practical data processing steps involved. An overview of 22 applications of InSAR to forest mapping and monitoring is given, covering tree bole volume 23 and biomass, forest types and land cover, fire scars, forest thermal state and forest canopy 24