Observations and discussions of TanDEM-X interferogram spectra over rain forest

This paper reports about some SAR interferometric obervations over rainforest (in Brazil and Indonesia). The spectra of TanDEM-X interferograms exhibit a bimodal character, which can be explained by the fact that vertical components of the trees are present in the interferograms. This is explained by interpreting the periodogram as a histogram of the different slopes present in the scene. Simulations based on based on clouds of point scatterers are enough for a first modeling of the observations. It is possible to show -theoretically and with the support of simulations- that a horizontally homogeneous forest model is not able to justify our observations. This analysis has been made possible by the characteristics of the TanDEM-X system: high resolution, almost no temporal decorrelation and relatively small heights of ambiguity.