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Quantifying the scales of spatial variation in gravel beds using terrestrial and airborne laser scanning data

Quantifying the scales of spatial variation in gravel beds using terrestrial and airborne laser scanning data
Quantifying the scales of spatial variation in gravel beds using terrestrial and airborne laser scanning data

Previous studies measured gravel bed surfaces by terrestrial laser scanning (TLS) and close-range photogrammetry suggested the presence of at least two different scales of spatial variation in gravel bed surfaces. This study investigated the spatial variation of airborne laser scanning (ALS) point clouds acquired in gravel bed. Due to the large footprint of ALS systems, a smoother surface is expected, but there exists some uncertainty over the precise scale of ALS measurement (hereafter referred to as the spatial support). As a result, we applied the regularization method, which is a variogram upscaling approach, to investigate the true support of ALS data. The regularization results suggested that the gravel bed surface described by the ALS is much smoother than expected in terms of the ALS reported measurement scale. Moreover, we applied the factorial kriging (FK) method, which allows mapping of different scales of variation present in the data separately (different from ordinary kriging which produces a single map), to obtain the river bed topography at each scale of spatial variation. We found that the short-range and long-range FK maps of the TLS-derived DSMs were able to highlight the edges of gravels and clusters of gravels, respectively. The long-range FK maps of the ALS data shows a pattern of gravel-bed clusters and aggregations of gravels. However, the short-range FK maps of the ALS data produced noisy maps, due to the smoothing effect. This analysis, thus, shows clearly that ALS data may be insufficient for geomorphological and hydraulic engineering applications that require the resolution of individual gravels.

factorial kriging, geomorphology, laser scanning, upscaling, variogram
607-617
Huang, Guo Hao
865d0c88-481a-4731-84af-71bb742a2ac7
Atkinson, Peter M.
96e96579-56fe-424d-a21c-17b6eed13b0b
Wang, Chi Kuei
80f2e43b-93bb-486d-961d-a167b9519011
Huang, Guo Hao
865d0c88-481a-4731-84af-71bb742a2ac7
Atkinson, Peter M.
96e96579-56fe-424d-a21c-17b6eed13b0b
Wang, Chi Kuei
80f2e43b-93bb-486d-961d-a167b9519011

Huang, Guo Hao, Atkinson, Peter M. and Wang, Chi Kuei (2018) Quantifying the scales of spatial variation in gravel beds using terrestrial and airborne laser scanning data. Open Geosciences, 10 (1), 607-617. (doi:10.1515/geo-2018-0048).

Record type: Article

Abstract

Previous studies measured gravel bed surfaces by terrestrial laser scanning (TLS) and close-range photogrammetry suggested the presence of at least two different scales of spatial variation in gravel bed surfaces. This study investigated the spatial variation of airborne laser scanning (ALS) point clouds acquired in gravel bed. Due to the large footprint of ALS systems, a smoother surface is expected, but there exists some uncertainty over the precise scale of ALS measurement (hereafter referred to as the spatial support). As a result, we applied the regularization method, which is a variogram upscaling approach, to investigate the true support of ALS data. The regularization results suggested that the gravel bed surface described by the ALS is much smoother than expected in terms of the ALS reported measurement scale. Moreover, we applied the factorial kriging (FK) method, which allows mapping of different scales of variation present in the data separately (different from ordinary kriging which produces a single map), to obtain the river bed topography at each scale of spatial variation. We found that the short-range and long-range FK maps of the TLS-derived DSMs were able to highlight the edges of gravels and clusters of gravels, respectively. The long-range FK maps of the ALS data shows a pattern of gravel-bed clusters and aggregations of gravels. However, the short-range FK maps of the ALS data produced noisy maps, due to the smoothing effect. This analysis, thus, shows clearly that ALS data may be insufficient for geomorphological and hydraulic engineering applications that require the resolution of individual gravels.

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Quantifying the scales of spatial variation in gravel beds using terrestrial and airborne laser scanning data - Version of Record
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Accepted/In Press date: 27 September 2018
e-pub ahead of print date: 30 October 2018
Keywords: factorial kriging, geomorphology, laser scanning, upscaling, variogram

Identifiers

Local EPrints ID: 426259
URI: http://eprints.soton.ac.uk/id/eprint/426259
PURE UUID: 2e21ef5d-ae7f-4ecd-a394-d25f4f76798e
ORCID for Peter M. Atkinson: ORCID iD orcid.org/0000-0002-5489-6880

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Date deposited: 21 Nov 2018 17:30
Last modified: 07 Oct 2020 01:37

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Contributors

Author: Guo Hao Huang
Author: Peter M. Atkinson ORCID iD
Author: Chi Kuei Wang

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