Studies of Phase Center and Extinction Coefficient of Boreal Forest Using X- and L-band Polarimetric Interferometry Combined with Lidar Measurements

In this work we study L-band and X-band interferometric phase center location in boreal forest in order to assist height retrieval with POLinSAR methods. We complement interferometric L-band and X-band dataset with an accurate LIDAR measured terrain and canopy height model. The LIDAR measured model allows to calculate ground and treetop phase estimates and reveal the radar measured phase center location inside the canopy We show that for X-band, the interferometric phase center is mostly in the upper quarter of the canopy as predicted by Random Volume over Ground model, indicating that ground is not visible but attenuation is still rather low. We show that tree height estimation is feasible with one polarization X-band (TanDEM-X ) interferometry with simple methods when an accurate digital terrain model is available. At Lband the phase center is around half way of the canopy height and often lower, indicating that ground contribution is significant and attenuation is low. The phase center height follows well the treetop line, except for sparse forest.