[Coral-List] Coral-List Digest, Vol 105, Issue 12 - 3D Modelling Coral Reefs with GoPro

[Dennis Hubbard]

Hi Renata:

It is staggering how good this method has become. I have two questions, one
relating to future projects and the other related to comparing with past
data. Neither argues against using this powerful tool.

First, many of us work on smaller scales (or at least have) than is laid
out in "Accuracy and Precision of Habitat Structural Complexity Metrics
Derived from Underwater Photogrammetry". Can you provide a protocol and
recommend a low-cost camera that might be applicable to this method? My
thought would be to "fly" a vertical, diver-held camera over transects to
get rugosity within particular parts of the reef, relate that to what is
immediately on either side of a transect and then use either enlarged
single frames or on-bottom IDs for species.

Second, as so many of our present discussions center around changes between
"today" and reefs past, how do we reconcile higher-density data with older
surveys? Even with repetitive chain transects on the same transects,
rugosity with the old system will depend on how careful the researchers
were in fitting the chain over the surface. This creates inherent
inaccuracies that could be eliminated going forward. If, however, we wanted
to make long-term comparisons of rugosity along the lines of Alvarez et al,
I am guessing that we would see significant(and probably false) increases
in rugosity since 1970 if we compared older chain-transect data to  the
newer photogrammetric surveys.

I ask these questions because we plan to re-survey a reef we worked on in
1979. There are myriad issues with going back to a site where it is
difficult to constrain exact locations of 30-year old transects even with
good georeferencing of the profile across which they were located.

Best,

Dennis

On Sat, May 6, 2017 at 1:55 AM, Renata Ferrari Legorreta <
renata.ferraril at gmail.com> wrote:

> Dear Coral Listers,
>
> There have been several papers published during the last few years on how
> to create 3D models of coral colonies and coral reefs using off-the-shelf
> cameras and software.
>
> Here are a few links of the papers I found the most useful:
>
> Quantifying Multiscale Habitat Structural Complexity: A Cost-Effective
> Framework for Underwater 3D Modelling
> http://www.mdpi.com/2072-4292/8/2/113/html <http://www.mdpi.com/2072-
> 4292/8/2/113/html>
>
> Quantifying the response of structural complexity and community
> composition to environmental change in marine communities
> http://onlinelibrary.wiley.com/doi/10.1111/gcb.13197/abstract <
> http://onlinelibrary.wiley.com/doi/10.1111/gcb.13197/abstract>
>
> Accuracy and Precision of Habitat Structural Complexity Metrics Derived
> from Underwater Photogrammetry
> http://www.mdpi.com/2072-4292/7/12/15859/htm <http://www.mdpi.com/2072-
> 4292/7/12/15859/htm>
>
> End of the chain? Rugosity and fine-scale bathymetry from existing
> underwater digital imagery using structure-from-motion (SfM) technology
> https://link.springer.com/article/10.1007/s00338-016-1462-8 <
> https://link.springer.com/article/10.1007/s00338-016-1462-8>
>
>
> GoPros™ as an underwater photogrammetry tool for citizen science
> https://peerj.com/articles/1960/ <https://peerj.com/articles/1960/>
>
>
> All the best,
>
> Renata Ferrari
> www.3dreefs.org <http://www.3dreefs.org/>
>
>
>
> > On May 5, 2017, at 6:44 AM, coral-list-request at coral.aoml.noaa.gov
> wrote:
> >
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> > Today's Topics:
> >
> >
> >   2. 3D Modelling Coral Reefs with GoPro (Grace C. Young)
> >
> >
> >
> > ------------------------------
> >
> > Message: 2
> > Date: Thu, 4 May 2017 18:53:41 +0100
> > From: "Grace C. Young" <grace.young at some.ox.ac.uk>
> > Subject: [Coral-List] 3D Modelling Coral Reefs with GoPro
> > To: coral-list at coral.aoml.noaa.gov
> > Message-ID:
> >       <CAJz8Yq_+ocgphvHoye-k14BU2rqEoXtsmLrzqVaBQDNpyojTH
> g at mail.gmail.com>
> > Content-Type: text/plain; charset=UTF-8
> >
> > Dear Coral Listers,
> >
> > We published a methods for creating and analyzing 3D models of coral
> reefs
> > from GoPro footage to assess reef structural complexity:
> >
> >> http://journals.plos.org/plosone/article?id=10.1371/
> journal.pone.0175341
> >
> >
> > I'll be running workshops in various locations over the next several
> months
> > on how to make and analyze 3D models of underwater scenes. If you're
> > interested, please get in touch with me and/or fill out this
> > <https://goo.gl/forms/J3Kw7lTfHmvTV0GH2> form.
> > _____________
> > Grace C. Young ? University of Oxford
> > www.graceunderthesea.com
> > Twitter: @grace_h2o <https://twitter.com/grace_h2o>
> >
> >
> > -
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-- 
Dennis Hubbard
Chair, Dept of Geology-Oberlin College Oberlin OH 44074
(440) 775-8346

* "When you get on the wrong train.... every stop is the wrong stop"*
 Benjamin Stein: "*Ludes, A Ballad of the Drug and the Dream*"