Estimating Ground Elevation and Vegetation Characteristics in Coastal Salt Marshes Using UAV-Based LiDAR and Digital Aerial Photogrammetry
This study evaluates the skills of two types of drone-based point clouds, derived from LiDAR and photogrammetric techniques, in estimating ground elevation, vegetation height, and vegetation density on a highly vegetated salt marsh. The proposed formulation is calibrated and tested using data measur...
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| Autores principales: | , , , , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
MDPI AG
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/84522854d7fe47c3abd5aa370d479200 |
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| Sumario: | This study evaluates the skills of two types of drone-based point clouds, derived from LiDAR and photogrammetric techniques, in estimating ground elevation, vegetation height, and vegetation density on a highly vegetated salt marsh. The proposed formulation is calibrated and tested using data measured on a <i>Spartina alterniflora</i>-dominated salt marsh in Little Sapelo Island, USA. The method produces high-resolution (ground sampling distance = 0.40 m) maps of ground elevation and vegetation characteristics and captures the large gradients in the proximity of tidal creeks. Our results show that LiDAR-based techniques provide more accurate reconstructions of marsh vegetation (height: MAE<sub>VH</sub> = 12.6 cm and RMSE<sub>VH</sub> = 17.5 cm; density: MAE<sub>VD</sub> = 6.9 stems m<sup>−2</sup> and RMSE<sub>VD</sub> = 9.4 stems m<sup>−2</sup>) and morphology (MAE<sub>M</sub> = 4.2 cm; RMSE<sub>M</sub> = 5.9 cm) than Digital Aerial Photogrammetry (DAP) (MAE<sub>VH</sub> = 31.1 cm; RMSE<sub>VH</sub> = 38.1 cm; MAE<sub>VD</sub> = 12.7 stems m<sup>−2</sup>; RMSE<sub>VD</sub> = 16.6 stems m<sup>−2</sup>; MAE<sub>M</sub> = 11.3 cm; RMSE<sub>M</sub> = 17.2 cm). The accuracy of the classification procedure for vegetation calculation negligibly improves when RGB images are used as input parameters together with the LiDAR-UAV point cloud (MAE<sub>VH</sub> = 6.9 cm; RMSE<sub>VH</sub> = 9.4 cm; MAE<sub>VD</sub> = 10.0 stems m<sup>−2</sup>; RMSE<sub>VD</sub> = 14.0 stems m<sup>−2</sup>). However, it improves when used together with the DAP-UAV point cloud (MAE<sub>VH</sub> = 21.7 cm; RMSE<sub>VH</sub> = 25.8 cm; MAE<sub>VD</sub> = 15.2 stems m<sup>−2</sup>; RMSE<sub>VD</sub> = 18.7 stems m<sup>−2</sup>). Thus, we discourage using DAP-UAV-derived point clouds for high-resolution vegetation mapping of coastal areas, if not coupled with other data sources. |
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