The ground-truth about lidar-derived digital elevation models in coastal
wetland regions of the northern Gulf of Mexico
Abstract
Recent advances in the quality and availability of lidar permit high
spatial resolution in digital elevation models (DEMs). However,
large-scale lidar acquisitions may be flown during high tides, storm
events, and irregular tidal regimes leading to temporal change
differences, but ultimately the uneven penetration through dense
vegetation impacts the reality of ground surface positions. For the
low-gradient coastal land margin of the northern Gulf of Mexico, even a
small elevation bias (on the order of 0.1 m) can adversely affect
surface hydrodynamic model accuracy. Therefore, ground-truthing with a
vertical elevation adjustment is essential for robust biogeophysical
modeling. This study assessed measurement errors of lidar-derived DEM
datasets (1 m DEMs), developed in 2021. The DEM was evaluated for
distinct coastal wetlands, especially coastal marshes of Louisiana,
Mississippi, and Alabama. Error analysis was conducted using Real-Time
Kinematic (RTK) GPS to assess how well the lidar-derived elevations
represent the actual marsh surface (ground surface). The performance of
the temporally and spatially distinct lidar-derived elevation datasets
was evaluated over 7,000 elevation points measured between 2011-2021. We
also examined the relationship between measurement errors and vegetation
characteristics (marsh type, height, and percent cover). This
presentation will demonstrate our ongoing efforts to assess the
high-resolution lidar-derived elevations in coastal wetlands and discuss
the measurement errors.