Preprints
https://doi.org/10.5194/egusphere-2022-75
https://doi.org/10.5194/egusphere-2022-75
05 Apr 2022
 | 05 Apr 2022

Size, shape and orientation matter: fast and automatic measurement of grain geometries from 3D point clouds

Philippe Steer, Laure Guerit, Dimitri Lague, Alain Crave, and Aurélie Gourdon

Abstract. The grain-scale morphology of sediments and their size distribution inform on their transport history, are important factors controlling the efficiency of erosion and transport and control the quality of aquatic ecosystems. In turn, constraining the spatial evolution of the size and shape of grains can offer deep insights on the dynamics of erosion and sediment transport in coastal, hillslope and fluvial environments. However, the size distribution of sediments is generally assessed using insufficiently representative field measurements and determining the grain-scale shape of sediments remains a real challenge in geomorphology. Here, we determine the size distribution and grain-scale shape of sediments located in coastal and river environments with a new methodological approach based on the segmentation and geomorphological fitting of 3D point clouds. Point cloud segmentation into individual grains is performed using a watershed algorithm applied here to 3D point clouds. Once the grains are individualized into several sub-clouds, each grain-scale morphology is determined by fitting a 3D geometrical model applied to each sub-cloud. If different geometrical models can be conceived and tested, including cuboids and ellipsoids, this study focuses mostly on ellipsoids. A phase of results checking is then performed to remove grains showing a best-fitting model with a low level of confidence. The main benefits of this automatic and non-destructive method are that it provides access to 1) an un-biased estimate of surface grain-size distribution on a large range of scales, from centimeters to meters; 2) a very large number of data, only limited by the number of grains in the point-cloud dataset; 3) the 3D morphology of grains, in turn allowing to develop new metrics characterizing the size and shape of grains; and 4) the in-situ orientation and organization of grains and grain clusters. The main limit of this method is that it is only able to detect grains with a characteristic size greater than the resolution of the point cloud.

Journal article(s) based on this preprint

02 Dec 2022
| Highlight paper
Size, shape and orientation matter: fast and semi-automatic measurement of grain geometries from 3D point clouds
Philippe Steer, Laure Guerit, Dimitri Lague, Alain Crave, and Aurélie Gourdon
Earth Surf. Dynam., 10, 1211–1232, https://doi.org/10.5194/esurf-10-1211-2022,https://doi.org/10.5194/esurf-10-1211-2022, 2022
Short summary Editor

Philippe Steer et al.

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-75', Benjamin Purinton, 15 Apr 2022
  • RC2: 'Comment on egusphere-2022-75', Anonymous Referee #2, 10 May 2022
  • EC1: 'Comment on egusphere-2022-75', Rebecca Hodge, 19 May 2022
  • AC1: 'Response to comments on egusphere-2022-75', Philippe Steer, 21 Sep 2022

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-75', Benjamin Purinton, 15 Apr 2022
  • RC2: 'Comment on egusphere-2022-75', Anonymous Referee #2, 10 May 2022
  • EC1: 'Comment on egusphere-2022-75', Rebecca Hodge, 19 May 2022
  • AC1: 'Response to comments on egusphere-2022-75', Philippe Steer, 21 Sep 2022

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Philippe Steer on behalf of the Authors (21 Sep 2022)  Author's response   Author's tracked changes   Manuscript 
ED: Referee Nomination & Report Request started (03 Oct 2022) by Rebecca Hodge
RR by Benjamin Purinton (12 Oct 2022)
RR by Anonymous Referee #2 (21 Oct 2022)
ED: Publish subject to minor revisions (review by editor) (24 Oct 2022) by Rebecca Hodge
AR by Philippe Steer on behalf of the Authors (27 Oct 2022)  Author's response   Author's tracked changes   Manuscript 
ED: Publish as is (01 Nov 2022) by Rebecca Hodge
ED: Publish as is (08 Nov 2022) by Tom Coulthard (Editor)
AR by Philippe Steer on behalf of the Authors (09 Nov 2022)  Manuscript 

Journal article(s) based on this preprint

02 Dec 2022
| Highlight paper
Size, shape and orientation matter: fast and semi-automatic measurement of grain geometries from 3D point clouds
Philippe Steer, Laure Guerit, Dimitri Lague, Alain Crave, and Aurélie Gourdon
Earth Surf. Dynam., 10, 1211–1232, https://doi.org/10.5194/esurf-10-1211-2022,https://doi.org/10.5194/esurf-10-1211-2022, 2022
Short summary Editor

Philippe Steer et al.

Model code and software

G3Point v1.0 Philippe Steer https://github.com/philippesteer/G3Point

Philippe Steer et al.

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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

Understanding how sediment moves in rivers is fundamental to the shape of our landscapes and how they evolve. A key part of this understanding is measuring the size and shape of cobbles, pebbles and grains in the bed of a river. Often this measuring task is laborious and carried out by hand. However, this paper presents code and describes a method for measuring this using 3d point cloud data (from a laser scan for example) enabling the automation and rapid measurement.
Short summary
The morphology and size of sediments inform on their transport history, are important factors controlling the efficiency of erosion and transport, and control the quality of aquatic ecosystems. Here, we have developed a new software which aims at automatically identifying and measuring grains based on 3D topographic data of the surface of sediment deposits. This software is fast and efficient and offers a new avenue to measure the geometrical properties of large numbers of grains.