Sudoor Manthan- IIRS Science Portal
Authors- Ashutosh Bhardwaj, Hari Shankar Srivastava and Raghavendra Pratap Singh
Spaceborne LiDAR datasets are contributing immensely for the topographic, ice mass-balance and vegetation related studies. It provides a global view of changes occurring in elevation over Earth. CartoDEM Version 3 Release 1 openly accessible datasets are currently the most reliable datasets for the relatively plain regions in India. The study presents a comparative evaluation of the CartoDEM with respect to the two openly accessible space borne LiDAR datasets from the LiDAR sensors, namely: Advanced Topographic Laser Altimeter System (ATLAS) on-board the Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) and Global Ecosystem Dynamics Investigation (GEDI) over the International Space Station (ISS). GEDI operates using three Nd:YAG (neodymium-doped yttrium aluminum garnet) lasers, emitting 1064 nm light (242 Hz frequency), whereas ICESat-2 use six laser beams at 532 nm (10 KHz frequency). The difference or deviation were computed for the CartoDEM and the LiDAR footprint elevations for the two datasets namely, ICESat-2 and GEDI.
Figure 1. Depict footprints of the GEDI laser Beams over Moga region
Region of Moga district was considered for the evaluation as it has a cross-over of paths of GEDI, ISS (i.e. ground traces) providing sufficiently elevation data for the evaluation. The difference values were filtered for footprints with difference between 0 to 2.5 in the DEM and LiDAR elevation values. Besides this an overall estimate is also done for the elevation values obtained over the surface i.e. ground as well as the objects such as the trees or buildings. The RMSE is observed as 1.16m and 1.74m for ICESat-2 and GEDI dataset for the points/footprints on the terrain. Whereas considering similar parameters for the two datasets for the data filtering strategies, the RMSE is obtained as 1.78m and 5.48m for the ICESat-2 and GEDI footprints on the surface (terrain/object) respectively.
The study reveals that the CartoDEM is highly accurate in the plains when validated with respect to the ICESat-2 Spaceborne LiDAR datasets which work on the photon counting technique. Further, it is observed that the ICESat-2 performance is better than the GEDI mission for the terrain height. Thus it can be observed that the spaceborne LiDAR datasets from ICESat-2 can be utilized for validation of DEMs and can be useful for applications where an input of DEM is required for engineering or modelling applications.
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