A note on a computer-based system for theodolite tracking of cetaceans

Résumé

Theodolites represent a non-invasive shore-based tool for obtaining data on cetacean movement patterns, habitat use and behavioural disturbance. Despite the common use of theodolites as research tools, relatively few computer-based systems exist to assist researchers with collection of theodolite derived data and the analysis of such information. A recently developed computer program named ‘Pythagoras’, provides an efficient and user-friendly tool for collecting, managing and subsequent analysis of data obtained with theodolites. Pythagoras provides location of user-defined fix types (e.g. whales, dolphins, boats, etc.) and has a dynamic interface, that can be customised to fit site-specific research needs. Additional information (behaviour, group size and environmental conditions) can be stored with each theodolite fix. Tracking data are immediately available in the form of a real-time graphic representation. All collected data are stored in Microsoft Access and can be exported as Microsoft Excel, ArcInfo, Surfer, MATLAB, or delimited text file formats. An analysis module is included to calculate linearity, reorientation rate and leg speed for each track, and distance and orientation between two or more tracklines. Behavioural data are analysed for frequency, time intervals (i.e. blow interval), duration (i.e. surface time) and rate (number per minute) of particular behaviours. Several other computer-based theodolite systems are reviewed here to evaluate their potential benefits and limitations as a means of providing a basis for future developments.