Accounting for radiotelemetry signal flux in triangulation point estimation |
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Authors: | Shawn P Haskell Warren B Ballard |
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Institution: | (1) Department of Natural Resources Management, Texas Tech University, 102 Goddard Building, Lubbock, TX 79409-2125, USA |
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Abstract: | Triangulation by radiotelemetry is a method commonly used to estimate locations of wildlife. Despite the importance of the
accuracy of resulting location estimates, there has been little development and comparison of alternative methods for point-location
estimation for 25 years. Most methods assume that signal transmissions as they are received are consistent, but signal heterogeneity
and fluxing is common. Using data from a beacon study, we determined that a subjective ranking of confidence in the accuracy
of a signal was correlated with absolute bearing error. Using this factor and the distance from a telemetry station to the
error triangle incenter, we developed an algorithm to place a weighted point-location estimate in relative proximity to each
error triangle leg. We have termed this the weighted-incenter method. Despite previous findings that the major confidence
ellipse axis of Lenth’s maximum likelihood estimator (MLE) correlated best to linear distance error, our beacon test data
indicated that total bearing angle difference was the best single predictor of linear error with an optimal total angle of
about 100°. The new and intuitive weighted-incenter method offered some improvement over previous methods such as the MLE
estimator, but only with suboptimal angle bearings that may be common in field studies. By using a MATLAB function to produce
data for site-specific regression analyses, one can determine which method should produce the more accurate point-location
estimate for each triangulation observation. Further significance of this study for field biologists is discussed. |
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Keywords: | Accuracy Maximum likelihood Methods Weighted-incenter |
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