Integration of Alos PalSAR and LIDAR IceSAT Data in a Multistep Approach for Wide Area Biomass Mapping in Borneo
Quinones, Marcela1; Hokman, Dirk2
1SarVision, NETHERLANDS; 2Wageningen University, NETHERLANDS
Accurate wall to wall above ground biomass mapping approaches are required to address information needs on carbon distributions for the implementation of policies regarding reducing emissions from deforestation and degradation (REDD+). Accurate forest stratification and distribution of biomass data are some of the critical components needed for the forest carbon measurement and as basic components for national monitoring systems.
Regarding the use of active remote sensing sensors, SAR (synthetic Aperture Radar) systems have proven to be sensitive to above ground biomass until certain biomass levels, defined by the well know saturation effect. For the different radar frequencies and polarizations the saturation point varies from 100 ton/ha to 250 ton /ha which are biomass values lower that what can be found in most of the tropical forests. Using radar-based technology, new approaches are needed that can provide accurate biomass estimations on a wider biomass range. So far different techniques are being explore to overcome the saturation effect: Other biomass mapping approaches using radar polarimetry were also analyzed in the past for tropical areas in general restrictions on the mapping procedures using direct biomass estimations from radar data inversions were found to be affected by forest structure and soil moisture conditions.
In this paper we present a methodology for wall to wall biomass mapping using a multistep approach to integrate SAR data, field information and GLAS height derived data. This new approach proposes first an stratification of the radar data into vegetation structural classes based on radar classification techniques. Second: the coupling of the distributions of the radar backscatter values per cover type class and the distributions of the heights derived from GLAS-LIDAR for the whole island of Borneo. Field observations for different vegetation structural types are used to constraint the GLAS LIDAR data and to exclude outlier. Heights are inverted into biomass values using available allometric equations from the literature. Validation is done using biomass estimates from the field. This approach is for the first time applied over wide areas at a 50 m. Resolution in the island of Borneo. In addition aadvanced techniques for the pre-processing of the radar data like the radiometric correction and relief correction to reduce topographic effects are applied to the data and the wide area mapping methodology developed before. This work has been undertaken in part within the framework of the ALOS Kyoto & Carbon Initiative, an international research collaboration led by the Japanese space agency JAXA.. ALOS PALSAR data have been generously provided by JAXA Earth Observation Research Centre (EORC). Collaboration with Utrecht University in the collection and processing of (local) biomass measurement data was essential for the validation of the final biomass map. SarVision provided methodological advice on biomass measurement in the field and support the collection of biomass field data based. 100 plots were measured in the field collected in representative vegetation strata in East Kalimantan combining the methodology developed by ICRAF and FAO.