References

Ocean Science

Ocean Sci.

1812-0792

Copernicus Publications

Göttingen, Germany

10.5194/os-9-461-2013

A new 3-D modelling method to extract subtransect dimensions from underwater videos

Fillinger

¹ Funke

Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Am Alten Hafen 26, 27568 Bremerhaven, Germany

16 04 2013

9 2 461 476

2013

This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/

This article is available from https://os.copernicus.org/articles/9/461/2013/os-9-461-2013.html

The full text article is available as a PDF file from https://os.copernicus.org/articles/9/461/2013/os-9-461-2013.pdf

Underwater video transects have become a common tool for quantitative analysis of the seafloor. However a major difficulty remains in the accurate determination of the area surveyed as underwater navigation can be unreliable and image scaling does not always compensate for distortions due to perspective and topography. Depending on the camera set-up and available instruments, different methods of surface measurement are applied, which make it difficult to compare data obtained by different vehicles. 3-D modelling of the seafloor based on 2-D video data and a reference scale can be used to compute subtransect dimensions. Focussing on the length of the subtransect, the data obtained from 3-D models created with the software PhotoModeler Scanner are compared with those determined from underwater acoustic positioning (ultra short baseline, USBL) and bottom tracking (Doppler velocity log, DVL). 3-D model building and scaling was successfully conducted on all three tested set-ups and the distortion of the reference scales due to substrate roughness was identified as the main source of imprecision. Acoustic positioning was generally inaccurate and bottom tracking unreliable on rough terrain. Subtransect lengths assessed with PhotoModeler were on average 20% longer than those derived from acoustic positioning due to the higher spatial resolution and the inclusion of slope. On a high relief wall bottom tracking and 3-D modelling yielded similar results. At present, 3-D modelling is the most powerful, albeit the most time-consuming, method for accurate determination of video subtransect dimensions.

References 1

Althaus, F., Williams, A., Schlacher, T. A., Kloser, R. J., Green, M. A., Barker, B. A., Bax, N. J., Brodie, P., and Schlacher-Hoenlinger, M. A.: Impacts of bottom trawling on deep-coral ecosystems of seamounts are long-lasting, Mar. Ecol.-Prog. Ser., 397, 279–294, https://doi.org/<a href="http://dx.doi.org/10.3354/meps08248">10.3354/meps08248</a>, 2009.

Amado-Filho, G. M., Pereira-Filho, G. H., Bahia, R. G., Abrantes, D. P., Veras, P. C., and Matheus, Z.: Occurrence and distribution of rhodolith beds on the {F}ernando de {N}oronha {A}rchipelago of {B}razil, Aquat. Bot., 101, 41–45, https://doi.org/<a href="http://dx.doi.org/10.1016/j.aquabot.2012.03.016">10.1016/j.aquabot.2012.03.016</a>, 2012.

Ambrose, W. G., von Quillfeldt, C., Clough, L. M., Tilney, P. V. R., and Tucker, T.: The sub-ice algal community in the {C}hukchi sea: large- and small-scale patterns of abundance based on images from a remotely operated vehicle, Polar Biol., 28, 784–795, https://doi.org/<a href="http://dx.doi.org/10.1007/s00300-005-0002-8">10.1007/s00300-005-0002-8</a>, 2005.

Anderson, T. J. and Yoklavich, M. M.: Multiscale habitat associations of deepwater demersal fishes off central {C}alifornia, Fish. B. NOAA, 105, 168–179, <a href="http://fishbull.noaa.gov/1052/anderson.pdf">http://fishbull.noaa.gov/1052/anderson.pdf</a>, 2007.

Auster, P. J., Stewart, L. L., and Sprunk, H.: Scientific imaging with {ROV}s: tools and techniques, Mar. Technol. Soc. J., 23, 16–20, 1989.

Baker, K. D., Haedrich, R. L., Snelgrove, P. V. R., Wareham, V. E., Edinger, E. N., and Gilkinson, K. D.: Small-scale patterns of deep-sea fish distributions and assemblages of the G}rand {B}anks, {N}ewfoundland continental slope, Deep-Sea Res. Pt. I, 65, 171–188, https://doi.org/<a href="http://dx.doi.org/10.1016/j.dsr.2012.03.012">10.1016/j.dsr.2012.03.012</a>, 2012{{a}.

Baker, K. D., Wareham, V. E., Snelgrove, P. V. R., Haedrich, R. L., Fifield, D. A., Edinger, E. N., and Gilkinson, K. D.: Distributional patterns of deep-sea coral assemblages in three submarine canyons off N}ewfoundland, {C}anada, Mar. Ecol.-Prog. Ser., 445, 235–249, https://doi.org/<a href="http://dx.doi.org/10.3354/meps09448">10.3354/meps09448</a>, 2012{{b}.

Barry, J. P. and Baxter, C. H.: Survey design considerations for deep-sea benthic communities using {ROV}s, Mar. Technol. Soc. J., 26, 20–26, 1993.

Beall, C., Lawrence, B. J., Ila, V., and Dellaert, F.: 3D reconstruction of underwater structures, in: The IEEE/RJS 2010 International Conference on Intelligent Robots and Systems (IROS2010), Taipei, Taiwan, 18–22 October 2010, 4418–4423, https://doi.org/<a href="http://dx.doi.org/10.1109/IROS.2010.5649213">10.1109/IROS.2010.5649213</a>, 2010.

Bland, J. M. and Altman, D. G.: Statistical method for assessing agreement between two methods of clinical measurement, Lancet, 327, 307–310, https://doi.org/<a href="http://dx.doi.org/10.1016/S0140-6736(86)90837-8">10.1016/S0140-6736(86)90837-8</a>, 1986.

Bonin, F., Burguera, A., and Oliver, G.: Imaging systems for advanced underwater vehicles, J. Marit. Res., 3, 65–86, 2011.

Brandou, V. and Allais, A. G. and Perrier, M. and Malis, E. and Rives, P. and Sarrazin, J. and Sarradin, P. M.: 3{D} reconstruction of natural underwater scenes using the stereovision system IRIS, in: Proceedings of OCEANS'07 IEEE Conference, Aberdeen, Scotland, 18–21 June 2007, 1–6, https://doi.org/<a href="http://dx.doi.org/10.1109/OCEANSE.2007.4302315">10.1109/OCEANSE.2007.4302315</a>, 2005.

Bythell, J. C., Pan, P., and Lee, J.: Three-dimensional morphometric measurements of reef corals using underwater photogrammetry techniques, Coral Reefs, 20, 193–199, https://doi.org/<a href="http://dx.doi.org/10.1007/s003380100157">10.1007/s003380100157</a>, 2001.

Carleton, J. H. and Done, T. J.: Quantitative video sampling of coral reef benthos: large-scale application, Coral Reefs, 14, 35–46, https://doi.org/<a href="http://dx.doi.org/10.1007/BF00304070">10.1007/BF00304070</a>, 1995.

Chevaldonné, P. and Jollivet, D.: Videoscopic study of deep-sea hydrothermal vent alvinellid polychaete populations: biomass estimation and behaviour, Mar. Ecol.-Prog. Ser., 95, 251–262, https://doi.org/<a href="http://dx.doi.org/10.3354/meps095251">10.3354/meps095251</a>, 1993.

Chu, J. W. F. and Leys, S. P.: High resolution mapping of community structure in three glass sponge reefs ({P}orifera, {H}exactinellida), Mar. Ecol.-Prog. Ser., 417, 97–113, https://doi.org/<a href="http://dx.doi.org/10.3354/meps08794">10.3354/meps08794</a>, 2010.

Cocito, S., Sgorbini, S., Peirano, A., and Valle, M.: 3{D} reconstruction of biological objects using underwater video technique and image processing, J. Exp. Mar. Biol. Ecol., 297, 57–70, https://doi.org/<a href="http://dx.doi.org/10.1016/S0022-0981(03)00369-1">10.1016/S0022-0981(03)00369-1</a>, 2003.

Cranmer, T. L., Ruhl, H. A., Baldwin, R. J., and Kaufmann, R. S.: Spatial and temporal variation in the abundance, distribution and population structure of epibenthic megafauna in {P}ort {F}oster, {D}eception {I}sland, Deep-Sea Res. Pt. II, 50, 1821–1842, https://doi.org/<a href="http://dx.doi.org/10.1016/S0967-0645(03)00093-6">10.1016/S0967-0645(03)00093-6</a>, 2003.

Cuvelier, D., Sarrazin, J., Colaco, A., Copley, J., Desbruyères, D., Glover, A. G., Tyler, P., and Santos, S. R.: Distribution and spatial variation of hydrothermal faunal assemblages at {L}ucky {S}trike ({M}id-{A}tlantic {R}idge) revealed by high-resolution video image analysis, Deep-Sea Res. Pt. I, 56, 2026–2040, https://doi.org/<a href="http://dx.doi.org/10.1016/j.dsr.2009.06.006">10.1016/j.dsr.2009.06.006</a>, 2009.

de Bruyn, P. J. N., Bester, M. N., Carlini, A. R., and Oosthuizen, W. C.: How to weigh an elephant seal with one finger: a simple three-dimensional photogrammetric application, Aquat. Biol., 5, 31–39, https://doi.org/<a href="http://dx.doi.org/10.3354/ab00135">10.3354/ab00135</a>, 2009.

Dolan, M. F. J., Grehan, A. J., Guinan, J. C., and Brown, C.: Modelling the local distribution of cold-water corals in relation to bathymetric variables: adding spatial context to deep-sea video data, Deep-Sea Res. Pt. I, 55, 1564–1579, https://doi.org/<a href="http://dx.doi.org/10.1016/j.dsr.2008.06.010">10.1016/j.dsr.2008.06.010</a>, 2008.

Dowdeswell, J. A., Evans, J., Mugford, R., Griffiths, G., McPhail, S., Millard, N., Stevenson, P., Brandon, M. A., Banks, C., Heywood, K. J., Price, M. R., Dodd, P. A., Jenkins, A., Nicholls, K. W., Hayes, D., Abrahamsen, E. P., Tyler, P., Bett, B., Jones, D., Wadhams, P., Wilkinson, J. P., Stansfield, K., and Ackley, S.: Autonomous underwater vehicles ({AUVs}) and investigations of the ice-ocean interface in {A}ntarctic and {A}rctic waters, J. Glaciol., 54, 661–672, https://doi.org/<a href="http://dx.doi.org/10.3189/002214308786570773">10.3189/002214308786570773</a>, 2008.

Ewins, N. J. and Pilgrim, D. A.: The evaluation of {P}hoto{M}odeler for use under water, in: The Fourth Underwater Science Symposium: Proceedings, Newcastle upon Tyne, UK, 19–20 November 1997, 135–145, 1997.

Gamroth, E., Kennedy, J., and Bradley, C.: Design and testing of an acoustic ranging technique applicable for an underwater positioning system, Underwater Technol., 29, 183–193, https://doi.org/<a href="http://dx.doi.org/10.3723/ut.29.183">10.3723/ut.29.183</a>, 2011.

Garcia, R., Battle, J., and Cufi, X.: Positioning an underwater vehicle through image mosaicking, in: Proceedings of the 2001 IEEE International Conference on Robotics & Automation, Seoul, Korea, 21–25 May 2001, 2779–2784, https://doi.org/<a href="http://dx.doi.org/10.1109/ROBOT.2001.933043">10.1109/ROBOT.2001.933043</a>, 2001.

Gratwicke, B. and Speight, M. R.: The relationship between fish species richness, abundance and habitat complexity in a range of shallow tropical marine habitats, J. Fish Biol., 66, 650–667, https://doi.org/<a href="http://dx.doi.org/10.1111/j.0022-1112.2005.00629.x">10.1111/j.0022-1112.2005.00629.x</a>, 2005.

Green, J. and Gainsford, M.: Evaluation of underwater surveying techniques, Int. J. Naut. Archaeol., 32, 252–261, https://doi.org/<a href="http://dx.doi.org/10.1016/j.ijna.2003.08.007">10.1016/j.ijna.2003.08.007</a>, 2003.

Green, J., Matthews, S., and Turanli, T.: Underwater archaeological surveying using {P}hoto{M}odeler, {V}irtual{M}apper: different applications for different problems, Int. J. Naut. Archaeol., 31, 283–292, https://doi.org/<a href="http://dx.doi.org/10.1006/ijna.2002.1041">10.1006/ijna.2002.1041</a>, 2002.

Guinan, J., Grehan, A. J., Dolan, M. F. J., and Brown, C.: Quantifying relationships between video observations of cold-water coral cover and seafloor features in {R}ockall {T}rough, west of {I}reland, Mar. Ecol.-Prog. Ser., 375, 125–138, https://doi.org/<a href="http://dx.doi.org/10.3354/meps07739">10.3354/meps07739</a>, 2009.

Gutt, J. and Starmans, A.: Quantification of iceberg impact and benthic recolonisation patterns in the {W}eddell {S}ea ({A}ntarctica), Polar Biol., 24, 615–619, https://doi.org/<a href="http://dx.doi.org/10.1007/s003000100263">10.1007/s003000100263</a>, 2001.

Huetten, E. and Greinert, J.: Software controlled guidance, recording and post-processing of seafloor observations by ROV and other towed devices: The software package OFOP, Geophys. Res. Abstr., 10, EGU2008-A-03088, 2008.

Jerosch, K., L{ü}dtke, A., Schl{ü}ter, M., and Ioannidis, G. T.: Automatic content-based analysis of georeferenced image data: Detection of <i>Beggiatoa</i> mats in seafloor video mosaics from the {H}åkon {M}osby Mud Volcano, Comput. Geosci., 33, 202–218, https://doi.org/<a href="http://dx.doi.org/10.1016/j.cageo.2006.06.014">10.1016/j.cageo.2006.06.014</a>, 2007.

Jones, D. O. B., Hudson, I. R., and Bett, B. J.: Effects of physical disturbance on the cold-water megafaunal communities of the {F}aroe–{S}hetland {C}hannel, Mar. Ecol.-Prog. Ser., 319, 43–54, https://doi.org/<a href="http://dx.doi.org/10.3354/meps319043">10.3354/meps319043</a>, 2006.

Jones, D. O. B., Bett, B. J., Wynn, R. B., and Masson, D. G.: The use of towed camera platforms in deep-water science, Underwater Technol., 28, 41–50, https://doi.org/<a href="http://dx.doi.org/10.3723/ut.28.041">10.3723/ut.28.041</a>, 2009.

Karpov, K. A., Lauermann, A., Bergen, M., and Prall, M.: Accuracy and precision of measurements of transect length and width made with a remotely operated vehicle, Mar. Technol. Soc. J., 40, 79–85, https://doi.org/<a href="http://dx.doi.org/10.4031/002533206787353196">10.4031/002533206787353196</a>, 2006.

Karpov, K. A., Bergen, M., and Geibel, J. J.: Monitoring fish in {C}alifornia {C}hannel {I}slands marine protected areas with a remotely operated vehicle: the first five years, Mar. Ecol.-Prog. Ser., 453, 159–172, https://doi.org/<a href="http://dx.doi.org/10.3354/meps09629">10.3354/meps09629</a>, 2012.

Kinsey, J. C. and Whitcomb, L. L.: Preliminary field experience with the DVLNAV integrated navigation system for oceanographic submersibles, Control Eng. Pract., 12, 1541–1549, https://doi.org/<a href="http://dx.doi.org/10.1016/j.conengprac.2003.12.010">10.1016/j.conengprac.2003.12.010</a>, 2004.

Kinsey, J. C., Eustice, R. M., and Whitcomb, L. L.: A survey of underwater vehicle navigation: recent advances and new challenges, in: Proceedings of the IFAC Conference of Manoeuvering and Control of Marine Craft, Lisbon, Portugal, 20–22 September 2006, 2006.

Kocak, D. M., Jagielo, T. H., Wallace, F., and Kloske, J.: Remote sensing using laser projection photogrammetry for underwater surveys, in: 2004 IEEE International Geoscience and Remote Sensing Symposium Proceedings (IGARSS 2004), Anchorage, Alaska, 20–24 September 2004, 1451–1454, https://doi.org/<a href="http://dx.doi.org/10.1109/IGARSS.2004.1368693">10.1109/IGARSS.2004.1368693</a>, 2004.

Kocak, D. M., Dalgleish, F. R., Caimi, F. M., and Schechner, Y. Y.: A focus on recent developments and trends in underwater imaging, Mar. Technol. Soc. J., 42, 52–67, 2008.

Laudien, J. and Orchard, J. B.: The significance of depth and substratum incline for the structure of a hard bottom sublittoral community in glacial {K}ongsfjorden ({S}valbard, {A}rctic) – an underwater imagery approach, Polar Biol., 35, 1057–1072, https://doi.org/<a href="http://dx.doi.org/10.1007/s00300-011-1153-4">10.1007/s00300-011-1153-4</a>, 2012.

Lindsay, D. J., Yoshida, H., Uemura, T., Yamamoto, H., Ishibashi, S., Nishikawa, J., Reimer, J. D., Beaman, R. J., Fitzpatrick, R., Fujikura, K., and Maruyama, T.: The {u}ntethered {r}emotely {o}perated {v}ehicle {PICASSO}-1 and its deployment from chartered dive vessels for deep sea surveys off {O}kinawa, {J}apan, and {O}sprey {R}eef, {C}oral {S}ea, {A}ustralia, Mar. Technol. Soc. J., 46, 20–32, https://doi.org/<a href="http://dx.doi.org/10.4031/MTSJ.46.4.3">10.4031/MTSJ.46.4.3</a>, 2012.

Mandelbrot, B.: How long is the coast of {B}ritain? {S}tatistical self-similarity and fractional dimension, Science, 156, 636–638, https://doi.org/<a href="http://dx.doi.org/10.1126/science.156.3775.636">10.1126/science.156.3775.636</a>, 1967.

Parry, D. M., Nickell, L. A., Kendall, M. A., Burrows, M. T., Pilgrim, D. A., and Jones, M. B.: Comparison of abundance and spatial distribution of burrowing megafauna from diver and remotely operated vehicle observations, Mar. Ecol.-Prog. Ser., 244, 89–93, https://doi.org/<a href="http://dx.doi.org/10.3354/meps244089">10.3354/meps244089</a>, 2002.

Parry, D. M., Kendall, M. A., Pilgrim, D. A., and Jones, M. B.: Identification of patch structure within marine benthic landscapes using a remotely operated vehicle, J. Exp. Mar. Biol. Ecol., 285–286, 497–511, https://doi.org/<a href="http://dx.doi.org/10.1016/S0022-0981(02)00546-4">10.1016/S0022-0981(02)00546-4</a>, 2003.

Patterson, W. F. I., Dance, M. A., and Addis, D. T.: Development of a remotely operated vehicle based methodology to estimate fish community structure at artificial reef sites in the northern {G}ulf of {M}exico, in: Proceedings of the 61st Gulf and Caribbean Fisheries Institute, Gosier, Guadeloupe, French West Indies, 10–14 November 2008, 263–270, 2009.

Pilgrim, D. A., Parry, D. M., Jones, M. B., and Kendall, M. A.: ROV image scaling with laser spot patterns, Underwater Technol., 24, 93–103, https://doi.org/<a href="http://dx.doi.org/10.3723/175605400783259684">10.3723/175605400783259684</a>, 2000.

Pinkard, D. R., Kocak, D. M., and Butler, J. L.: Use of a video and laser system to quantify transect area for remotely operated vehicle ({ROV}) rockfish and abalone surveys, in: Oceans 2005 Proceedings of MTS/IEEE Conference, Washington DC, USA, 18–23 September 2005, 2824–2829, https://doi.org/<a href="http://dx.doi.org/10.1109/OCEANS.2005.1640203">10.1109/OCEANS.2005.1640203</a>, 2005.

Pizarro, O. and Eustice, R. and Singh, H.: Large area 3{D} reconstruction from underwater surveys, in: Oceans 2004. Proceeding of MTTS/IEEE TECHNO-OCEAN '04 Conference, Kobe, Japan, 9–12 November 2004, 2, 678–687 https://doi.org/<a href="http://dx.doi.org/10.1109/OCEANS.2004.1405509">10.1109/OCEANS.2004.1405509</a>, 2004.

Pollio, J.: Applications of underwater photogrammetry, Mar. Technol. Soc. J., 40, 34–51, https://doi.org/<a href="http://dx.doi.org/10.4031/002533206787353411">10.4031/002533206787353411</a>, 1969.

Post, A. L., O'Brien, P. E., Beaman, R. J., Riddle, M. J., and De Santis, L.: Physical control on deep water coral communities on the G}eorge {V {L}and slope, {E}ast {A}ntarctica, Antarct. Sci., 22, 371–378, https://doi.org/<a href="http://dx.doi.org/10.1017/S0954102010000180">10.1017/S0954102010000180</a>, 2010.

Post, A. L., Beaman, R. J., O'Brien, P. E., Eléaume, M., and Riddle, M. J.: Community structure and benthic habitats across the G}eorge {V {S}helf, {E}ast {A}ntarctica: trends through space and time, Deep-Sea Res. Pt. II, 58, 105–118, https://doi.org/<a href="http://dx.doi.org/10.1016/j.dsr2.2010.05.020">10.1016/j.dsr2.2010.05.020</a>, 2011.

Richter, C., Wunsch, M., Rasheed, M., K{ö}tter, I., and Badran, M. I.: Endoscopic exploration of {R}ed {S}ea coral reefs reveals dense populations of cavity-dwelling sponges, Nature, 413, 726–730, https://doi.org/<a href="http://dx.doi.org/10.1038/35099547">10.1038/35099547</a>, 2001.

Ruhl, H. A.: Abundance and size distribution dynamics of abyssal epibenthic megafauna in the {N}ortheast {P}acific, Ecology, 88, 1250–1262, https://doi.org/<a href="http://dx.doi.org/10.1890/06-0890">10.1890/06-0890</a>, 2007.

Schettini, R. and Corchs, S.: Underwater image processing: state of the art of restoration and image enhancement methods, EURASIP J. Adv. Sig. Pr., 2010, 746 052, https://doi.org/<a href="http://dx.doi.org/10.1155/2010/746052">10.1155/2010/746052</a>, 2010.

Sedlazeck, A., K{ö}ser, K., and Koch, R.: 3{D} reconstruction based on underwater video from ROV {K}iel 6000 considering underwater imaging conditions, in: Proceedings of the IEEE Oceans 2009 Conference, Bremen, Germany, 11–14 May 2010, 1–10, https://doi.org/<a href="http://dx.doi.org/10.1109/OCEANSE.2009.5278305">10.1109/OCEANSE.2009.5278305</a>, 2009.

Shortis, M. R., Seager, J. W., Williams, A., Barker, B. A., and Sherlock, M.: Using stereo-video for deep water benthic habitat surveys, Mar. Technol. Soc. J., 42, 28–37, https://doi.org/<a href="http://dx.doi.org/10.4031/002533208787157624">10.4031/002533208787157624</a>, 2008.

Sievers, J. and Bennat, H.: Reference systems of maps and geographic information systems of Antarctica, Antarct. Sci., 1, 351–362, 1989.

Smith, C. R. and Hamilton, S. C.: Epibenthic megafauna of a bathyal basin off southern {C}alifornia: patterns of abundance, biomass and dispersion, Deep Sea Res. Pt A, 30, 907–928, https://doi.org/<a href="http://dx.doi.org/10.1016/0198-0149(83)90048-1">10.1016/0198-0149(83)90048-1</a>, 1983.

Smith, C. R., Grange, L. J., Honig, D. L., Naudts, L., Huber, B., Guidi, L., and Domack, E.: A large population of king crabs in {P}almer {D}eep on the west {A}ntarctic {P}eninsula shelf and potential invasive impacts, P. R. Soc. B, 279, 1017–1026, https://doi.org/<a href="http://dx.doi.org/10.1098/rspb.2011.1496">10.1098/rspb.2011.1496</a>, 2012.

Snyder, J.: Doppler {V}elocity {L}og ({DVL}) navigation for observation-class {ROV}s, in: Proceedings of the MTS/IEEEE Oceans 2010 Conference, Seattle, Waschington, USA, 18–23 September 2010, 1–9, https://doi.org/<a href="http://dx.doi.org/10.1109/OCEANS.2010.5664561">10.1109/OCEANS.2010.5664561</a>, 2010.

Söffker, M., Sloman, K. A., and Hall Spencer, J. M.: In situ observation of fish associated with coral reefs off {I}reland, Deep-Sea Res. Pt. I, 58, 818–825, https://doi.org/<a href="http://dx.doi.org/10.1016/j.dsr.2011.06.002">10.1016/j.dsr.2011.06.002</a>, 2011.

Solan, M., Germano, J. D., Rhoads, D. C., Smith, C., Michaud, E., Parry, D., Wenzh{ö}fer, F., Kennedy, B., Henriques, C., Battle, E., Carey, D., Iocco, L., Valente, R., Watson, J., and Rosenberg, R.: Towards a greater understanding of pattern, scale and process in marine benthic systems: a picture is worth a thousand worms, J. Exp. Mar. Biol. Ecol., 285–286, 313–338, https://doi.org/<a href="http://dx.doi.org/10.1016/S0022-0981(02)00535-X">10.1016/S0022-0981(02)00535-X</a>, 2003.

Stierhoff, K. L., Neuman, M., and Butler, J. L.: On the road to extinction? {P}opulation declines of the endangered white abalone, <i>Haliotis sorenseni</i>, Biol. Conserv., 152, 46–52, https://doi.org/<a href="http://dx.doi.org/10.1016/j.biocon.2012.03.013">10.1016/j.biocon.2012.03.013</a>, 2012.

Tissot, B. N.: Video analysis, experimental design and database management of submersible-based habitat studies, in: Marine habitat mapping technology for Alaska, edited by: Reynolds, J. R. and Greene, H. G., University of Alaska, Fairbanks, 157–167, 2008.

Tissot, B. N., Hixon, M., and Stein, D.: Habitat-based submersible assessment of macroinvertebrate and groundfish assemblages at {H}eceta {B}ank, {O}regon, from 1988 to 1990, J. Exp. Mar. Biol. Ecol., 352, 50–64, https://doi.org/<a href="http://dx.doi.org/10.1016/j.jembe.2007.06.032">10.1016/j.jembe.2007.06.032</a>, 2007.

Wakefield, W. W. and Genin, A.: The use of a {C}anadian (perspective) grid in deep-sea photography, Deep-Sea Res. Pt. I, 34, 469–478, https://doi.org/<a href="http://dx.doi.org/10.1016/0198-0149(87)90148-8">10.1016/0198-0149(87)90148-8</a>, 1987.

Wilson, S. K., Graham, N. A. J., and Polunin, N. V. C.: Appraisal of visual assessment of habitat complexity and benthic composition on coral reefs, Mar. Biol., 151, 1069–1076, https://doi.org/<a href="http://dx.doi.org/10.1007/s00227-006-0538-3">10.1007/s00227-006-0538-3</a>, 2007.

Wunsch, M. and Richter, C.: The {C}ave{C}am-an endoscopic underwater videosystem for the exploration of cryptic habitats, Mar. Ecol.-Prog. Ser., 169, 277–282, https://doi.org/<a href="http://dx.doi.org/10.3354/meps169277">10.3354/meps169277</a>, 1998.