Synthetic Aperture Radar for tropical savanna inventory and vegetation height retrieval

Iain Woodhouse, Neil Stuart, I.D. Cameron, K. M. Viergever, E.D. Wallington, D. Moss

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

This paper investigates the potential use of Synthetic Aperture Radar (SAR) for savanna inventory and biomass estimation at a test site located within the Hillbank savanna of the Rio Bravo Conservation Management Area (RBCMA), the second largest protected area in Belize. Airborne SAR provides a key opportunity for studying savannas, potentially providing information upon vegetation structure and canopy heights at high spatial resolutions. Two commercially available airborne X-band SAR products were utilised: an ortho rectified image (ORRI) of radar response intensity (backscatter) and a first return Interferometric SAR (InSAR) derived digital surface model (DSM) of the vegetation. Landcover interpretation from aerial photography is a widely used tool by land managers. In this study visual interpretation of the ORRI and DSM proved capable of delimiting the extent of pine woodland areas within the savanna using characteristic canopy height and backscatter intensity signatures for the assemblage. Upon comparison against reference data the interpretation successfully identified 80% of woodland plots from surrounding assemblages. Studies have shown SAR interferometry (InSAR) to have the potential for estimating forest height and biomass (e.g. Askne et al, 1997), it has yet to be widely applied to savanna formations. Here tree height estimation for an area of savanna woodland was investigated. Woodland heights were estimated from the difference between canopy heights (DSM) and the underlying topography. In the absence of a suitable ground surface model, one was created using traditional ground survey techniques. Retrieved woodland heights showed little relationship when compared to test plots (R2=0.061). These poor results were somewhat expected, and may be a result of low tree density, SAR geometry and subsequent edge effects, leading to substantial reductions in the scattering phase centre height.
Original languageEnglish
Title of host publicationGlobal developments in environmental earth orbservation from space. Proceedings of the 25th EARSeL Symposium, Porto, Portugal, 2005
Pages391-400
Number of pages10
Publication statusPublished - 2006

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