The potential of ALOS PALSAR backscatter and InSAR coherence for forest growing stock volume estimation in Central Siberia

Abstract

Abstract The full potential of ALOS PALSAR L-band interferometric (InSAR) coherence data for the estimation of forest growing stock volume ( GSV ) in the boreal forest has rarely been investigated. Moreover, ALOS PALSAR backscatter and InSAR coherence have yet to be used together to delineate GSV . Due to the observation strategy and the high acquisition success rate over Eurasia, a large amount of high quality ALOS PALSAR L-band data is available over Siberia. Consequently, this paper investigates the capability of ALOS PALSAR backscatter and InSAR coherence for the estimation of GSV in Central Siberia, Russia. The potential of backscatter and coherence are directly compared using the same inventory data. Altogether, 87 PALSAR images are used and eleven forest inventory sites are investigated. Based on this large dataset it was observed that InSAR coherence acquired in frozen conditions offers the highest potential for GSV estimation. The saturation level for single coherence images was on average 230 m 3 /ha, with an average R 2 between coherence and GSV of 0.58. PALSAR backscatter acquired in unfrozen conditions could also estimate GSV ; however, the saturation levels (75–100 m 3 /ha) and the average R 2 (0.42–0.48) were lower. HV backscatter offered only a slightly greater potential than HH backscatter. A simple inversion approach aiming at the delineation of forest GSV maps based on the multitemporal SAR data was developed and applied to five forest inventory sites. This approach combines HV backscatter data acquired in unfrozen conditions and InSAR coherence data acquired in frozen conditions. In general, the produced maps feature a corrected relative RMSE corr of 2 between inventory data and SAR data based maps varied between 0.54 and 0.83.