title: Camera Calibration for Water-Biota Research: The Projected Area of Vegetation.
abstract: Imaging systems have an indisputable role in revealing vegetation posture under diverse flow conditions, image sequences being generated with off the shelf digital cameras. Such sensors are cheap but introduce a range of distortion effects, a trait only marginally tackled in hydraulic studies focusing on water-vegetation dependencies. This paper aims to bridge this gap by presenting a simple calibration method to remove both camera lens distortion and refractive effects of water. The effectiveness of the method is illustrated using the variable projected area, computed for both simple and complex shaped objects. Results demonstrate the significance of correcting images using a combined lens distortion and refraction model, prior to determining projected areas and further data analysis. Use of this technique is expected to increase data reliability for future work on vegetated channels.
authors.affiliation: School of Civil and Building Engineering, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK. r.wackrow@lboro.ac.uk.
authors.forename: Rene
authors.initials: R
authors.lastname: Wackrow
authors.affiliation: School of Civil and Building Engineering, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK. e.a.ferreira@lboro.ac.uk.
authors.forename: Edgar
authors.initials: E
authors.lastname: Ferreira
authors.affiliation: School of Civil and Building Engineering, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK. j.h.Chandler@lboro.ac.uk.
authors.forename: Jim
authors.initials: J
authors.lastname: Chandler
authors.affiliation: School of Civil and Building Engineering, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK. k.shiono@lboro.ac.uk.
authors.forename: Koji
authors.initials: K
authors.lastname: Shiono
mesh_terms: D059001:Aquatic Organisms / Q000502:physiology*; D019723:Endoscopes; D004867:Equipment Design; D010780:Photogrammetry / Q000295:instrumentation* / Q000379:methods / Q000592:standards; D010944:Plants / Q000033:anatomy & histology*; D014867:Water / Q000737:chemistry
chemical_list: D014867:Water
keywords: eco-hydraulics; flow visualization and imaging; laboratory studies; photogrammetry; plants reconfiguration; underwater imaging; vegetated flows