Silvilaser 2019 - Poster Presentations »
Overview of MOLI Mission to Estimate Forest Biomass
It is important to have precise information about forest volume and area to evaluate forest biomass contribution as a carbon dioxide sink in the global carbon cycle. However, IPCC AR5 reports mentioned that the error in such estimates is still large. Spaceborne L-band SAR derives forest biomass empirically based on the relationship between the biomass and observed data, but the L-band signal saturates for dense tropical forests (i.e., over 100 t/ha). Forest canopy height is a significant factor in evaluating its biomass and can be observed by lidar using remote sensing techniques without signal saturation, so measuring canopy height from space will lead to a better understanding of the global carbon cycle. Japan Aerospace Exploration Agency (JAXA) has begun a study using space-based lidar to measure forest canopy height and biomass called Multi-footprint Observation Lidar and Imager (MOLI). MOLI uses dual beams with footprints small and close enough to determine ground slope, called “Multi-footprint” method. Previous studies to estimate canopy height and above ground biomass using ICESat/GLAS data reported that terrain relief in GLAS footprints affects accuracy of canopy height data considerably. MOLI’s “Multi-footprint” is useful for correcting estimation errors of canopy height and above ground biomass. Another feature of MOLI is that a three-band imager (green, red, and near-infrared) can determine where lidar is pointing and to measure the vegetation index at the same time. The MOLI mission provides product data about canopy height and above ground biomass density for each footprint. Improving MOLI’s data accuracies will require a better waveform analysis algorithm. On the other hand, it is difficult to obtain ground information from lidar waveforms observed for forests with high canopy cover ratio using conventional peak-fitting techniques. So, we try to solve this problem using novel algorithm such as machine leaning. This presentation will introduce the MOLI mission and an algorithm for converting observation raw data into product data. The authors have also conducted airborne-lidar experiments for preliminary testing of the validity of multi-footprint lidar and the imager to be used in MOLI’s observations and analyze the results of the experiment.