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    The advancing role of Global Positioning System (GPS) technology in ecology has made studies of animal movement possible for larger and more vagile species. A simple field test revealed that lengths of GPS-based movement data were strongly biased (P<0.001) by effects of forest canopy. Global Positioning System error added an average of 27.5% additional length to tracks recorded under high canopy, while adding only 8.5% to open-canopy tracks, thus biasing comparisons of track length or tortuosity among habitat types. Other studies may incur different levels of bias depending on GPS sampling rates. Ninety-nine percent of track errors under high canopy were ≤7.98 m of the true path; this value can be used to set the scale-threshold at which movements are attributed to error and not biologically interpreted. This bias should be considered before interpreting GPS-based animal movement data.

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    DeCesare, Nicholas J.; Squires, John R.; Kolbe, Jay A. 2005. Effect of forest canopy on GPS-based movement data. Wildlife Society Bulletin. 33(3): 935-941.


    animal movement, forest canopy closure, Global Positioning System, GPS error, GPStracking, snow-tracking, tortuosity

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