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Plankton 3D tracking: the importance of camera calibration in stereo computer vision systems

Author:
  • Giuseppe Bianco
  • Mikael Ekvall
  • Johan Bäckman
  • Lars-Anders Hansson
Publishing year: 2013
Language: English
Pages: 278-286
Publication/Series: Limnology and Oceanography: Methods
Volume: 11
Document type: Journal article
Publisher: Wiley-Blackwell

Abstract english

Computer vision applications are very useful to study animal movements, but due to their intrinsic complexity they are challenging to design, implement, and use properly. We here describe a calibration procedure for a laboratory stereo vision system for tracking zooplankton in three dimensions (3D). We demonstrate the crucial importance of using a correct calibration for proper interpretation of animal swimming tracks. We also address the effect of the air-water shift phase in the calibration procedure. Actually, not performing a proper calibration caused an average positional error of more than 25 body-lengths in the investigated animal Daphnia magna. Furthermore, we evaluate the different outcomes of using 2D and 3D tracks obtained with a calibrated stereo vision system and show that although 2D tracking might be sufficient in some cases, the method was in our study unable to give information of swimming path geometry and underestimated the speed by 25%. Finally, we discuss consequences for biologically relevant questions when an incorrect methodology is used and strongly recommend that future studies provide detailed descriptions of the framework used for calibration to allow for comparisons between different studies.

Keywords

  • Biological Sciences

Other

Published
  • BECC
  • CAnMove
  • ISSN: 1541-5856
Mikael Ekvall
E-mail: mikael.ekvall [at] biochemistry.lu.se

Doctoral student

Aquatic ecology

+46 46 222 40 80

E-C122

50

Centre for Animal Movement Research
Evolutionary Ecology, Department of Biology
Ecology building S-223 62 Lund Sweden