On forest height retrieval from spaceborne X-band interferometric SAR images under variable seasonal conditions

This paper discusses the possibility to use spaceborne X-band radar interferometry for forest height mapping. In our previous works was shown that airborne X-band SAR interferometry combined with accurate ground elevation model can provide good estimates of boreal forest height. In order to apply this technique to spaceborne SAR images, temporal variability of the scattering and lower signal to noise ratio of speceborne images should be taken into acount. In this work, a set of 10 TanDEM-X SAR satellite image pairs, acquired during summer and autumn 2011 over southern Finland, was used to evaluate the potential tree height retrieval performance and temporal stability of the method. The obtained results are compared to our previous studies on tree height retrieval with airborne E-SAR instrument of DLR in the same area. Our results show, that spaceborne TanDEM-X and TerraSAR-X satellite image pairs are suitable for forest height retrieval, but as expected, the accuracy of the method is lower than in the case of airborne measurement. Also the radar signal penetration depth into the forest varies seasonally and this variation should be taken into account when estimating tree height with SAR interferometry.