A new point cloud processing method unveiled hidden coastal boulders from deep vegetation

Nakata, Koki; Yanagisawa, Hideaki; Goto, Kazuhisa

doi:10.1038/s41598-023-37985-2

Cited by 4 publications

(2 citation statements)

References 40 publications

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“…Neely & DiBiase, 2020), coasts (e.g. Nakata et al, 2023;Naylor et al, 2016) and extra-terrestrial settings (e.g. Mangold et al, 2021;Roberts et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

How big is a boulder? The importance of boulder definition choice in earth science research and river management

Mason,

Polvi

2024

Earth Surf Processes Landf

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Boulders are globally widespread and influence processes across many landscapes including hillslopes, coasts, rivers and extra‐terrestrial settings. Boulders are described as particles, sufficiently large, that they have a disproportionate effect on the surrounding landscape. Moving beyond this conceptual definition, however, requires a somewhat arbitrary decision of how to define a minimum boulder size. The implications of boulder definition on study findings are rarely considered. We investigate the suitability of five boulder definitions, two based on fixed sizes: (1) 0.26 m and (2) 1 m, and three definitions which vary based on system characteristics: (3) grain mobility, (4) grain protrusion and (5) surface grain size distribution (> 84th percentile, D84). We consider the impact of definition on calculated boulder metrics, and, for the >1m and >D84 definitions, their association with channel and catchment characteristics across 20 boulder‐bed streams in northern Sweden. We also surveyed river managers responsible for restoring these rivers, to gain a practitioner insight on boulder size definition. We found that boulder definition matters; for metrics relating to the number or density of boulders, the >D84 and >1m size definitions were negatively correlated. Surveys indicated the importance of communicating boulder definition. We conclude that, whilst the best choice of boulder size definition will vary based on the questions of interest and techniques employed, evaluating the implications of the chosen boulder size definition and communicating the reasoning behind boulder definition choice is crucial.

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“…Neely & DiBiase, 2020), coasts (e.g. Nakata et al, 2023;Naylor et al, 2016) and extra-terrestrial settings (e.g. Mangold et al, 2021;Roberts et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

How big is a boulder? The importance of boulder definition choice in earth science research and river management

Mason,

Polvi

2024

Earth Surf Processes Landf

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“…Beaty, 1989;Neely & DiBiase, 2020), coasts (e.g. Naylor et al, 2016;Nakata et al, 2023), and extra-terrestrial settings (e.g. Roberts et al, 2012;Mangold et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

How big is a boulder? Evaluating fixed and process-based definitions for boulders

Mason¹,

Polvi²

2023

Preprint

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Boulders are globally widespread and influence landscape processes across hillslopes, coasts, rivers and extra-terrestrial settings. Boulders are described as particles, sufficiently large, that the movement of an individual grain promotes substantial geomorphic change. Moving beyond this conceptual definition, however, requires a somewhat arbitrary decision of how to define a minimum boulder size. Furthermore, the implications of boulder definition on study findings are rarely considered. We compare two lower thresholds for boulder size; a fixed boulder minimum diameter (> 1 m) and a variable diameter relative to the surface grain size distribution (> 84th percentile). We consider the impact of definition on measured boulder metrics, and their association with channel and catchment characteristics across 20 boulder-bed streams in northern Sweden. We also surveyed the river managers responsible for restoring these rivers, to gain a practitioner insight on boulder size definition. Definition choice resulted in fundamental differences in boulder metrics; metrics describing the number or density of boulders were negatively correlated. Using these two studies, we explore boulder definition in earth sciences, including the application of fixed definitions and those relative to grain size or system power. We emphasise the importance of evaluating the implications of the chosen boulder size definition, and communicating the reasoning behind boulder definitions and these implications. We discuss the implication of boulder size definition choice and provide guidelines for future studies seeking a process-based definition of boulders.

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Quantification of the spatial distribution of individual mangrove tree species derived from LiDAR point clouds

Kasai,

Yanagisawa,

Goto

2024

Prog Earth Planet Sci

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Mangrove forests have unquestionably high environmental and ecological value. Mangrove trees are believed to have habitat zonation that is controlled mainly by the relative sea level. However, earlier discussions of mangrove habitats have remained limited in terms of their quality and quantity because of a lack of high-resolution spatial information of microtopography and trees. To clarify mangrove habitability over a wide forest area, we compounded mobile laser scanning (MLS) and aerial laser scanning (ALS) LiDAR dataset of the Miyara River mangrove on Ishigaki Island, Okinawa, Japan. The MLS provided sub-canopy data, while the unmanned aerial vehicle ALS data mainly provided a point cloud of the canopy. We corrected point clouds and combined these data. The results indicated that ALS is unable to reconstruct the microtopography of the dense mangrove area well. Moreover, tree species were not identifiable from the ALS data. However, by applying MLS to the mangrove forest, we obtained high-resolution microtopography and tree information inside the forest, although the measurement area was limited to comparison with ALS. By combining ALS and MLS point clouds, 3D point clouds of the forest were well reconstructed. From these point clouds, a high-resolution digital elevation model was created. Subsequently, we segmented trees individually from composite MLS point clouds and identified each tree species. Consequently, the spatial distribution of thousands of mangrove trees was reconstructed at the Miyara River mouth. The spatial distribution of mangrove tree species together with earlier aerial photographs suggests that mangrove species have been segregated in accordance with changes in their elevation and environment over 40 years. Our findings suggest that the distribution of the species changed sensitively along with dynamic variation of the microtopography.

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A new point cloud processing method unveiled hidden coastal boulders from deep vegetation

Cited by 4 publications

References 40 publications

How big is a boulder? The importance of boulder definition choice in earth science research and river management

How big is a boulder? The importance of boulder definition choice in earth science research and river management

How big is a boulder? Evaluating fixed and process-based definitions for boulders

Quantification of the spatial distribution of individual mangrove tree species derived from LiDAR point clouds

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