title: Area Estimation of Deep-Sea Surfaces from Oblique Still Images.
abstract: Estimating the area of seabed surfaces from pictures or videos is an important problem in seafloor surveys. This task is complex to achieve with moving platforms such as submersibles, towed or remotely operated vehicles (ROV), where the recording camera is typically not static and provides an oblique view of the seafloor. A new method for obtaining seabed surface area estimates is presented here, using the classical set up of two laser devices fixed to the ROV frame projecting two parallel lines over the seabed. By combining lengths measured directly from the image containing the laser lines, the area of seabed surfaces is estimated, as well as the camera's distance to the seabed, pan and tilt angles. The only parameters required are the distance between the parallel laser lines and the camera's horizontal and vertical angles of view. The method was validated with a controlled in situ experiment using a deep-sea ROV, yielding an area estimate error of 1.5%. Further applications and generalizations of the method are discussed, with emphasis on deep-sea applications.
authors.affiliation: Task Group for the Extension of the Continental Shelf (EMEPC), Paço de Arcos, Portugal.
authors.forename: Frederico Carvalho
authors.initials: FC
authors.lastname: Dias
authors.affiliation: Task Group for the Extension of the Continental Shelf (EMEPC), Paço de Arcos, Portugal; MARE-Marine and Environmental Sciences Centre, Departamento de Oceanografia e Pescas, Centre of IMAR, Universidade dos Açores, Horta, Portugal.
authors.forename: José
authors.initials: J
authors.lastname: Gomes-Pereira
authors.affiliation: Task Group for the Extension of the Continental Shelf (EMEPC), Paço de Arcos, Portugal.
authors.forename: Inês
authors.initials: I
authors.lastname: Tojeira
authors.affiliation: Task Group for the Extension of the Continental Shelf (EMEPC), Paço de Arcos, Portugal.
authors.forename: Miguel
authors.initials: M
authors.lastname: Souto
authors.affiliation: Task Group for the Extension of the Continental Shelf (EMEPC), Paço de Arcos, Portugal.
authors.forename: Andreia
authors.initials: A
authors.lastname: Afonso
authors.affiliation: Task Group for the Extension of the Continental Shelf (EMEPC), Paço de Arcos, Portugal.
authors.forename: António
authors.initials: A
authors.lastname: Calado
authors.affiliation: Task Group for the Extension of the Continental Shelf (EMEPC), Paço de Arcos, Portugal.
authors.forename: Pedro
authors.initials: P
authors.lastname: Madureira
authors.affiliation: Task Group for the Extension of the Continental Shelf (EMEPC), Paço de Arcos, Portugal.
authors.forename: Aldino
authors.initials: A
authors.lastname: Campos
mesh_terms: D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D007834:Lasers; D055620:Optical Phenomena; D010781:Photography / Q000295:instrumentation; D015203:Reproducibility of Results; D012623:Seawater; D013499:Surface Properties; D035501:Uncertainty