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Remote Sens. 2012, 4(8), 2210-2235; doi:10.3390/rs4082210
Article

Influence of Surface Topography on ICESat/GLAS Forest Height Estimation and Waveform Shape

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Received: 16 May 2012; in revised form: 12 July 2012 / Accepted: 18 July 2012 / Published: 26 July 2012
(This article belongs to the Special Issue Laser Scanning in Forests)
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Abstract: This study explores ICESat/GLAS waveform data in Thuringian Forest, a low mountain range located in central Germany. Lidar remote sensing has been proven to directly derive tree height as a key variable of forest structure. The GLAS signal is, however, very sensitive to surface topography because of the large footprint size. This study therefore focuses on forests in a mountainous area to assess the potential of GLAS data to derive terrain elevation and tree height. The work enhances the empirical knowledge about the interaction between GLAS waveform and landscape structure regarding a special temperate forest site with a complex terrain. An algorithm to retrieve tree height directly from GLA01 waveform data is proposed and compared to an approach using GLA14 Gaussian parameters. The results revealed that GLAS height estimates were accurate for areas with a slope up to 10° whereas waveforms of areas above 15° were problematic. Slopes between 10–15° have been found to be a critical crossover. Further, different waveform shape types and landscape structure classes were developed as a new possibility to explore the waveform in its whole structure. Based on the detailed analysis of some waveform examples, it could be demonstrated that the waveform shape can be regarded as a product of the complex interaction between surface and canopy structure. Consequently, there is a great variety of waveform shapes which in turn considerably hampers GLAS tree height extraction in areas with steep slopes and complex forest conditions.
Keywords: ICESat/GLAS; waveform lidar; forest structure; tree height; surface topography; mountainous area ICESat/GLAS; waveform lidar; forest structure; tree height; surface topography; mountainous area
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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MDPI and ACS Style

Hilbert, C.; Schmullius, C. Influence of Surface Topography on ICESat/GLAS Forest Height Estimation and Waveform Shape. Remote Sens. 2012, 4, 2210-2235.

AMA Style

Hilbert C, Schmullius C. Influence of Surface Topography on ICESat/GLAS Forest Height Estimation and Waveform Shape. Remote Sensing. 2012; 4(8):2210-2235.

Chicago/Turabian Style

Hilbert, Claudia; Schmullius, Christiane. 2012. "Influence of Surface Topography on ICESat/GLAS Forest Height Estimation and Waveform Shape." Remote Sens. 4, no. 8: 2210-2235.


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