Computer systems for photo-identification and theodolite tracking of cetaceans

Abstract

Two separate computer-based systems were evaluated for two different methodological techniques (photo-identification and theodolite tracking) of cetacean research. The photo-identification program, Finscan, was evaluated to determine the feasibility of identifying individuals based on digital representatives of photographs and to assess the efficiency of the program compared to a traditional processing approach. Parameters of image quality and individual distinctiveness were measured by multiple judges to provide "true" quality and distinctiveness values. The image quality and distinctiveness values assisted in providing further insights into user-based and program performance testing. Using a database of 1375 images, judges could not classify individual distinctiveness independent of image quality. Furthermore, based on the digital representation of the photograph, image quality and individual distinctiveness parameters were found to affect the ability of experienced judges to identify individuals. Three matching methods (curve, string, and hybrid), which were used to describe dorsal fin features and present users with a structured list of potential matches to a query image, were evaluated to determine the best overall approach to match individuals. Matching methods varied with identifiable features of different species, where large curvature was found to affect curve matching, but string matching was more resistant to curvature of the dorsal fin. Hybrid matching was found to produce intermediate results between curve and string methods. The theodolite program, Pythagoras, assist researchers in collecting, managing, and analyzing theodolite-derived data. The program calculates distance, bearing, and geographic location of user-defined fix types and displays the information in real-time. The system calculates leg speed, linearity, reorientation rate within a trackline, and distance and relative orientation between two or more tracklines. Pythagoras was also found to provide similar and different capabilities compared to other theodolite programs available for cetacean research. Both computer systems, Finscan and Pythagoras, were found to provide useful platforms to assist in processing data from the field.