@article{fdi:010064125,
  title = {{L}ow-cost small action cameras in stereo generates accurate underwater measurements of fish},
  author = {{L}etessier, {T}. {B}. and {J}uhel, {J}ean-{B}aptiste and {V}igliola, {L}aurent and {M}eeuwig, {J}. {J}.},
  editor = {},
  language = {{ENG}},
  abstract = {{S}mall action cameras have received interest for use in underwater videography because of their low-cost, standardised housing, widespread availability and small size. {H}ere, we assess the capacity of {G}o{P}ro action cameras to provide accurate stereo-measurements of fish in comparison to the {S}ony handheld cameras that have traditionally been used for this purpose. {S}tandardised stereo-{G}o{P}ro and {S}ony systems were employed to capture measurements of known-length targets in a pool to explore the influence of the type of camera, distance to camera rig, angle to the optical axis and target speed on measurement accuracy. {T}he capacity to estimate fish length in situ was also compared by measuring the same fish on a coral reef with two baited remote underwater video systems, each fitted with both a {G}o{P}ro and a {S}ony camera system. {P}ool trials indicated that the {G}o{P}ros were generally less accurate than the {S}onys. {A}ccuracy decreased with increased angles and distance for both systems but remained reasonably low (<7.5%) at 5 m distance and 25 angle for {G}o{P}ros. {S}peed of target movement did not result in any consistent decrease in accuracy. {I}n situ measurements revealed a strong correlation ({R}-2 = 0.94) between {S}ony and {G}o{P}ro length measurements of the same individual fish, with a slope not different from 1 and an intercept not different from 0, suggesting that {G}o{P}ro measurement errors do not result in a consistent bias at the level of individual fish. {M}oreover, the investigation of kernel density functions of the length distribution of the entire fish assemblage indicated that difference in measurement accuracy becomes negligible for purposes of comparing population size structure. {W}e suggest a measurement protocol for the use of {G}o{P}ro stereo-camera systems that improves accuracy, where distance to target is limited to 5 m and angle to optical axis is restricted to 25 degrees. {F}or distances up to 7 m, angles should be restricted to 15 degrees. {T}his protocol supports the use of small action cameras such as the {G}o{P}ro system, providing reductions in cost and increases in effective sampling efforts, compared with traditional rigs based on relatively expensive handheld cameras.},
  keywords = {{B}ody size ; {L}ength ; {M}onitoring ; {S}tereo-photogrammetry ; {V}ideography},
  booktitle = {},
  journal = {{J}ournal of {E}xperimental {M}arine {B}iology and {E}cology},
  volume = {466},
  numero = {},
  pages = {120--126},
  ISSN = {0022-0981},
  year = {2015},
  DOI = {10.1016/j.jembe.2015.02.013},
  URL = {https://www.documentation.ird.fr/hor/fdi:010064125},
}