Measuring tree height using ERS-1 SAR interferometry

The “effective” tree height in a forested area may be retrieved using ERS-1 SAR interferometry and a DEM of the ground surface. Successful measurements are presented for a boreal forest in Sweden during winter conditions, whereas measurements of a rain forest in the Amazon were not successful. The authors´ results indicate that the perpendicular baseline should be in the range 200-300 m in order to be sensitive to the tree height and to avoid excessive baseline decorrelation. The latter may partly be compensated by wavenumber shift filtering but residual decorrelation remains due to temporal changes and a finite scattering layer thickness. A general equation for the coherence magnitude after wavenumber shift filtering is also given