文章基本信息

标题：Correcting Positional Errors in Shore-Based Theodolite Measurements of Animals at Sea
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作者：Ophélie Sagnol ; Femke Reitsma ; Christoph Richter 等
期刊名称：Journal of Marine Biology
印刷版ISSN：1687-9481
电子版ISSN：1687-949X
出版年度：2014
卷号：2014
页码：1-8
DOI：10.1155/2014/267917
出版社：Hindawi Publishing Corporation
摘要：Determining the position of animals at sea can be particularly difficult and yet, accurate range and position of animals at sea are essential to answer a wide range of biological questions. Shore-based theodolite techniques have been used in a number of studies to examine marine mammal movement patterns and habitat use, offering reliable position measurements. In this study we explored the accuracy of theodolite measurements by comparing positional information of the same objects using two independent techniques: a shore-based theodolite station and an onboard GPS over a range of 25 km from the shore-based station. The technique was developed to study the habitat use of sperm whales ( Physeter macrocephalus ) off Kaikoura, New Zealand. We observed that the position accuracy fell rapidly with an increase in range from the shore-based station. Results showed that the horizontal angle was accurately determined, but this was not the case for the vertical angle. We calibrated the position of objects at sea with a regression-based correction to fit the difference in distance between simultaneously recorded theodolite fixes and GPS positions. This approach revealed the necessity to calibrate theodolite measurements with objects at sea of known position.