Accuracy of Terrain Heights from Spaceborne Laser Altimetry in Brunei's
Tropical Peatlands
Abstract
Tropical peatlands are estimated to hold carbon stocks of 70 Pg C or
more as partly-decomposed organic matter, or peat. Peat may accumulate
over thousands of years into gently mounded deposits called peat domes
with a relief of several meters over distances of kilometers. The curved
shape of peat domes accounts for much of the carbon storage in these
landscapes, but their subtle topographic signal is difficult to measure.
As many of the world’s tropical peatlands are remote and inaccessible,
spaceborne laser altimetry data from missions such as NASA’s Global
Ecosystem Dynamics Investigation (GEDI) and the Advanced Topographic
Laser Altimeter System (ATLAS) instrument on the Ice, Cloud and land
Elevation Satellite-2 (ICESat-2) observatory could help to describe
these deposits. However, for better and for worse, tropical peatlands
may also support forests with high above-ground biomass—averages of
over 200 Mg C / ha have been reported—which increases their carbon
stocks but further complicates determination of their surface topography
using laser altimetry. In this work, we evaluate retrieval of ground
elevations and canopy metrics derived from GEDI waveform data, as well
as single-photon data from ATLAS, with reference to an airborne laser
scanning dataset covering an area of over 100 km^2 in the Belait
District of Brunei Darussalam. We find that despite infrequent ground
retrievals, with regularization these spaceborne platforms can provide
useful data for tropical peatland surface altimetry.