Digital Height Modeling (DHM) of Tropical Forests using Multi-frequency InSAR Methodology

The objective of this study was to verify how digital elevation models (DEM) built by P-band repeat pass synthetic aperture radar (SAR) interferometry (InSAR) and X band InSAR can be used for estimating a digital height model (DHM) of forested environments and assess its quality. P band signal penetrates towards the forest floor which potentially generates a ground level DEM. X band radar reflects on the top of the vegetation cover, so X band InSAR produces a digital surface model (DSM). The DSM-DEM difference is a map of the vegetation cover height, the DHM. The estimated DHM can be used for forest volume estimation over large areas and used for improving SAR image interpretation either in P or X band. In September 2000, the National Institute for Space Research of Brazil (INPE) and the Brazilian Army Cartographic Service Division (DSG) conducted a mission over the Tapajo acutes National Forest, Para acute State, Brazil when X and P band InSAR data was obtained. Extensive ground data collection, forest inventory, land cover identification and differential GPS altitude measurements was done over the area to permit proper results assessment. It was concluded that the estimated DHM has a good relationship with the vegetation cover height, (r²~0.96) estimated from forest parameters measured on the ground survey.