Estimating herbaceous aboveground biomass in Sahelian rangelands using
structure from motion data collected on the ground and by UAV
Abstract
1.Herbaceous aboveground biomass (HAB) is a key indicator of grassland
vegetation and indirect estimation tools, such as remote sensing
imagery, increase the potential for covering larger areas in a timely
and cost-efficient way. Structure from motion (SfM) is an image analysis
process that can create a 3D model from a set of images. 2: Computed
from UAV and ground camera measurements, the SfM potential to estimate
the herbaceous aboveground biomass in Sahelian rangelands was tested in
this study. Both UAV and ground camera recordings were used at three
different scales: temporal, landscape and national (across Senegal). All
images were processed using PIX4D software and were used to extract
vegetation indices and heights. 3: A random forest algorithm was used to
estimate the HAB and the average estimation errors were around 150 g.m-²
for fresh mass (20% relative error) and 60 g.m-² for dry mass (around
25% error). A comparison between different datasets revealed that the
estimates based on camera data were slightly more accurate than those
from UAV data. 4:It was also found that combining datasets across scales
for the same type of tool (UAV or camera) could be a useful option for
monitoring HAB in Sahelian rangelands or in other grassy ecosystem.