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Titel |
A new 3-D modelling method to extract subtransect dimensions from underwater videos |
VerfasserIn |
L. Fillinger, T. Funke |
Medientyp |
Artikel
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Sprache |
Englisch
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ISSN |
1812-0784
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Digitales Dokument |
URL |
Erschienen |
In: Ocean Science ; 9, no. 2 ; Nr. 9, no. 2 (2013-04-16), S.461-476 |
Datensatznummer |
250018048
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Publikation (Nr.) |
copernicus.org/os-9-461-2013.pdf |
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Zusammenfassung |
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. |
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