Abstract
With a planned launch no later than September 2018, the Ice, Cloud and land Elevation Satellite-2 (ICESat-2) will provide a global distribution of geodetic elevation measurements for both the terrain surface and relative canopy heights. The Advanced Topographic Laser Altimeter System (ATLAS) instrument on-board ICESat-2 is a LiDAR system sensitive to the photon level. The photon-counting technology has many advantages for space-based altimetry, but also has challenges, particularly with delineating the signal from background noise. As such, a current unknown facing the ecosystem community is the performance of ICESat-2 for terrain and canopy height retrievals. This paper aims to provide the science user community of ICESat-2 land/vegetation data products with a realistic understanding of the performance characteristics and potential uncertainties related to the vertical sampling error, which includes the error in the perceived height value and the measurement precision. Terrain and canopy heights from simulated ICESat-2 data are evaluated against the airborne LiDAR ground truth values to provide a baseline performance uncertainty for multiple ecosystems. Simulation results for wooded savanna and boreal forest result in a mean bias error and error uncertainty (precision) for terrain height retrievals at 0.06 m (0.24 m RMSE) and −0.13 m (0.77 m RMSE). In contrast, results over ecosystems with dense vegetation show terrain errors of 1.93 m (1.66 m RMSE) and 2.52 m (3.18 m RMSE), indicating problems extracting terrain height due to diminished ground returns. Simulated top of canopy heights from ICESat-2 underestimated true top of canopy returns for all types analyzed with errors ranging from 0.28 m (1.39 m RMSE) to 1.25 m (2.63 m RMSE). These results comprise a first step in a comprehensive evaluation of ICESat-2 anticipated performance. Future steps will include solar noise impact analysis and investigation into performance discrepancy between visible and near-infrared wavelengths.
Highlights
With a launch expected in the latter half of 2018, the ICESat-2 satellite will provide a global distribution of geodetic measurements from a space-based laser altimeter of both the terrain surface and relative canopy heights, which will provide a significant benefit to society through a variety of applications ranging from forest structural mapping to improved global digital terrain models
Evident from the results presented here, the deciduous hardwoods and tropical forest ecosystems will potentially see the largest errors associated with terrain height retrievals
These errors are most likely associated with the substantial extent of vegetated cover, as the signal received by the Advanced Topographic Laser Altimeter System (ATLAS) instrument is dominated with reflections from within the canopy rather than the ground surface, creating a difficult scenario for accurate terrain height estimation and subsequent canopy heights within the ATL08 product
Summary
With a launch expected in the latter half of 2018, the ICESat-2 satellite will provide a global distribution of geodetic measurements from a space-based laser altimeter of both the terrain surface and relative canopy heights, which will provide a significant benefit to society through a variety of applications ranging from forest structural mapping to improved global digital terrain models. The Earth’s land surface is a complex mosaic of geomorphic units and land cover types resulting in large variations in terrain height, slope, roughness, vegetation height and reflectance, often with the variations occurring over very small spatial scales. Documentation of these landscape properties is a first step in understanding the interplay between the formative processes and response to changing conditions. The accuracy of SRTM-derived heights range from 5–10 m, depending on the amount of topography and vegetation cover over a particular area [1,2]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
