Estimating Forest Stand Height in Savannakhet, Lao PDR Using InSAR and Backscatter Methods with L-Band SAR Data

Abstract:

Forest stand height (FSH), or average canopy height, serves as an important indicator for forest monitoring, providing information about potential habitat for different species, history of land use, the amount of above ground biomass for greenhouse gas emissions reporting, and estimating carbon storage. Synthetic Aperture Radar (SAR) data characterizes vegetation structure and moisture content independently of weather conditions. The SERVIR Global network and SilvaCarbon program collaborated to develop the SAR Handbook: Comprehensive Methodologies for Forest Monitoring and Biomass Estimation and accompanying series of workshops to increase the capacity of researchers and practitioners globally to take advantage of the unique information provided by SAR. This presentation showcases the application of the FSH estimation method described in Chapter 4 of the SAR Handbook. This method combines backscatter and interferometric SAR (InSAR) techniques utilizing the Advanced Land Observing Satellite Phased Array type L-band Synthetic Aperture Radar (ALOS PALSAR) and LiDAR data to estimate FSH in Savannakhet, Lao. The InSAR technique assumes that the greater the amount of change that occurs between two SAR observations separated by time, the taller the forest. The backscatter technique assumes that the scattering intensity in a forest stand increases with greater vegetation height, and thus more backscatter power is received by the sensor. The InSAR technique complements the backscatter technique, which saturates for vegetation above 10 m in height. The Savannakhet, Lao use case demonstrates the applicability of techniques utilizing L-band SAR data for estimating FSH in tropical forests and can be used as a springboard for use of L-band data from the NASA-ISRO SAR (NISAR) mission, launching in 2022.