Accuracy Assessment of GEDI Terrain Elevation and Canopy Height Estimates in European Temperate Forests: Influence of Environmental and Acquisition Parameters

Markus Adam,Christiane Schmullius,Mikhail Urbazaev,Clémence Dubois

doi:10.3390/rs12233948

Markus Adam, Christiane Schmullius + Show 2 more

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https://doi.org/10.3390/rs12233948

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Journal: Remote sensing	Publication Date: Dec 2, 2020
Citations: 78	License type: CC BY 4.0

Affiliation: Friedrich Schiller University Jena

Abstract

Lidar remote sensing has proven to be a powerful tool for estimating ground elevation, canopy height, and additional vegetation parameters, which in turn are valuable information for the investigation of ecosystems. Spaceborne lidar systems, like the Global Ecosystem Dynamics Investigation (GEDI), can deliver these height estimates on a near global scale. This paper analyzes the accuracy of the first version of GEDI ground elevation and canopy height estimates in two study areas with temperate forests in the Free State of Thuringia, central Germany. Digital terrain and canopy height models derived from airborne laser scanning data are used as reference heights. The influence of various environmental and acquisition parameters (e.g., canopy cover, terrain slope, beam type) on GEDI height metrics is assessed. The results show a consistently high accuracy of GEDI ground elevation estimates under most conditions, except for areas with steep slopes. GEDI canopy height estimates are less accurate and show a bigger influence of some of the included parameters, specifically slope, vegetation height, and beam sensitivity. A number of relatively high outliers (around 9–13% of the measurements) is present in both ground elevation and canopy height estimates, reducing the estimation precision. Still, it can be concluded that GEDI height metrics show promising results and have potential to be used as a basis for further investigations.

Highlights

Accurate information about ground elevation and canopy height are of great use in various scientific fields
The results of the analysis presented in this study show both similarities and differences to the results of comparable studies
Global Ecosystem Dynamics Investigation (GEDI) ground elevation metrics have a relatively high accuracy, with median digital terrain model (DTM)-differences below 30 cm. These values suggest an increased accuracy compared to the results from studies using other spaceborne lidar-based height metrics

Summary

Introduction

Accurate information about ground elevation and canopy height are of great use in various scientific fields. Light detection and ranging (lidar) is as a powerful tool for the acquisition of ground elevation and canopy height information on large scales, both in the form of airborne laser scanning (ALS) and spaceborne lidar. Its measurements were used to derive parameters like ground elevation [2,3], canopy height [4,5,6,7], aboveground biomass [8,9,10], and global canopy height maps [11,12] The results from these studies show a generally good accuracy of the derived metrics and present spaceborne lidar as a powerful tool for estimating ground elevation and vegetation parameters on large scales. GLAS was not originally build to derive vegetation structure, and some of its specifications (like the large footprint size of 70 m) are not ideal for these applications [13]

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