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Remote Sens. 2017, 9(8), 843; https://doi.org/10.3390/rs9080843

An Accuracy Assessment of Derived Digital Elevation Models from Terrestrial Laser Scanning in a Sub-Tropical Forested Environment

1
Joint Remote Sensing Research Program, School of Earth and Environmental Sciences, University of Queensland, St. Lucia, Brisbane 4067, Queensland, Australia
2
Department of Science, Information Technology and Innovation (DSITI) Remote Sensing Centre, Ecosciences Precinct, Brisbane 4001, Queensland, Australia
3
School of Science and Technology, University of New England, Armidale 2350, New South Wales, Australia
4
Department of Geographical Sciences, University of Maryland, College Park, MD 20742, USA
*
Author to whom correspondence should be addressed.
Academic Editor: Lars T. Waser
Received: 15 June 2017 / Revised: 28 July 2017 / Accepted: 9 August 2017 / Published: 14 August 2017
(This article belongs to the Section Forest Remote Sensing)
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Abstract

Forest structure attributes produced from terrestrial laser scanning (TLS) rely on normalisation of the point cloud values from sensor coordinates to height above ground. One method to do this is through the derivation of an accurate and repeatable digital elevation model (DEM) from the TLS point cloud that is used to adjust the height. The primary aim of this paper was to test a number of TLS scan configurations, filtering options and output DEM grid resolutions (from 0.02 m to 1.0 m) to define a best practice method for DEM generation in sub-tropical forest environments. The generated DEMs were compared to both total station (TS) spot heights and a 1-m DEM generated from airborne laser scanning (ALS) to assess accuracy. The comparison to TS spot heights found that a DEM produced using the minimum elevation (minimum Z value) from a point cloud derived from a single scan had mean errors >1 m for DEM grid resolutions <0.2 m at a 25-m plot radius. At a 1-m grid resolution, the mean error was 0.19 m. The addition of a filtering approach that combined a median filter with a progressive morphological filter and a global percentile filter was able to reduce mean error of the 0.02-m grid resolution DEM to 0.31 m at a 25-m plot radius using all returns. Using multiple scan positions to derive the DEM reduced the mean error for all DEM methods. Our results suggest that a simple minimum Z filtering DEM method using a single scan at the grid resolution of 1 m can produce mean errors <0.2 m, but for a small grid resolution, such as 0.02 m, a more complex filtering approach and multiple scan positions are required to reduced mean errors. The additional validation data provided by the 1-m ALS DEM showed that when using the combined filtering method on a point cloud derived from a single scan at the plot centre, errors between 0.1 and 0.5 m occurred in the TLS DEM for all tested grid resolutions at a plot radius of 25 m. These findings present a protocol for DEM production from TLS data at a range of grid resolutions and provide an overview of factors affecting DEMs produced from single and multiple TLS scan positions. View Full-Text
Keywords: terrestrial laser scanning; digital elevation model; ground; LiDAR; forest; accuracy terrestrial laser scanning; digital elevation model; ground; LiDAR; forest; accuracy
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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 (CC BY 4.0).
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Muir, J.; Goodwin, N.; Armston, J.; Phinn, S.; Scarth, P. An Accuracy Assessment of Derived Digital Elevation Models from Terrestrial Laser Scanning in a Sub-Tropical Forested Environment. Remote Sens. 2017, 9, 843.

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