Introducing <i>PebbleCounts</i>: a grain-sizing tool for photo surveys of dynamic gravel-bed rivers

Purinton, Benjamin; Bookhagen, Bodo

doi:https://doi.org/10.5194/esurf-7-859-2019

Articles | Volume 7, issue 3

https://doi.org/10.5194/esurf-7-859-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/esurf-7-859-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 7, issue 3

Research article

|

17 Sep 2019

Research article |

| 17 Sep 2019

Introducing PebbleCounts: a grain-sizing tool for photo surveys of dynamic gravel-bed rivers

Benjamin Purinton and Bodo Bookhagen

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Final revised paper (published on 17 Sep 2019)
Supplement to the final revised paper
Preprint (discussion started on 23 Apr 2019)
Supplement to the preprint

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

RC1: 'Review of Puriton and Bookhagen 2019.', Patrice Carbonneau, 16 May 2019
RC2: 'comments on the paper "PebbleCounts"', Pascal Allemand, 30 May 2019
AC1: 'Response to reviewers', Benjamin Purinton, 13 Jun 2019

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Benjamin Purinton on behalf of the Authors (13 Jun 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (24 Jun 2019) by Eric Lajeunesse

RR by Patrice Carbonneau (23 Jul 2019)

Suggestions for revision or reasons for rejection

The authors have done a good job of the revisions. With respect to my own recommendations, I only see some very minor corrections. In order of importance:

There remains significant issues with the question of the angle of views. First, top-down is a colloquial term and I remain firm that is should not be used in literature. Nadir is the correct term. Form most of the history of aerial imagery, there has always been error in the angle of acquisition. When aircraft, including drones, try to collect nadir data, there will still be fluctuations around the target angle of view. Having errors in that view is not a good reason to use the wrong nomenclature. If the authors are concerned that the camera mast setup induces error, then their images could be described as ‘slightly off-nadir’ or 'near-vertical' but nadir would still be fine because it is understood that no airborne camera can be controlled to have perfect orientation . This actually raises a question: To what extent are these images off-nadir? A number is not provided. In the current revision, there is in fact a problem of clarity in this case. When using the camera mast (or in the lab) are the authors deliberately trying to acquire images that are significantly oblique, i.e. actively tilting the camera off-nadir? If not, this is a nadir setup and the authors need to discuss the off-nadir component as a measurement error. This could in fact play in their favour by mitigating the doming effect in SfM-photogrammetry (See the James and Robson in ESPL, 2014). The authors need to:
1- Stop using the term top-down
2- Clarify if they are actively taking oblique imagery.

The authors have much improved the discussion of their errors in relation to other published work. But their refusal to provide a summary table is not justified nor is it reasonable. The authors are right that different papers report error differently, but that is not a good reason not to summarise information. There is abundant precedent for such tables in other similar works(see Dugdale et al in RRA on ‘Aerial Photosieving’). The point is to give a sense, even if qualitative, of relative performance. The textual discussion of this topic is very good. But, I repeat, please provided a summary table, many of your readers will appreciate the condensed information and better absorb your points in this manner.

The discussion of UAV applications is also much improved. But section 8.3.2 should be just 1 paragraph. The second paragraph repeats most of the ideas of the first and it seems like the first was dropped in without a proper reading of the second. This just needs to be merged and have repetitions smoothed out.

Patrice Carbonneau

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ED: Publish subject to minor revisions (review by editor) (08 Aug 2019) by Eric Lajeunesse

AR by Benjamin Purinton on behalf of the Authors (16 Aug 2019) Author's response Manuscript

ED: Publish as is (22 Aug 2019) by Eric Lajeunesse

ED: Publish as is (26 Aug 2019) by Tom Coulthard(Editor)

Short summary

We develop and test new methods for counting pebble-size distributions in photos of gravel-bed rivers. Our open-source algorithms provide good estimates in complex imagery from high-energy mountain rivers. We discuss methods of river cross-section photo collection and processing into seamless georeferenced imagery. Application of a semi-automated version of the algorithm in small patches can be used as validation data for upscaling to entire survey sites using a fully automated version.