Abstract |
- Consumer-grade GPS units are a staple of modern field ecology, but the relatively
large error radii reported by manufacturers (up to 10 m) ostensibly precludes their
utility in measuring fine-scale movement of small animals such as insects. Here
we demonstrate that for data collected at fine spatio-temporal scales, these devices
can produce exceptionally accurate data on step-length and movement patterns of
small animals. With an understanding of the properties of GPS error and how it
arises, it is possible, using a simple field protocol, to use consumer grade GPS units
to collect step-length data for the movement of small animals that introduces a
median error as small as 11 cm. These small error rates were measured in controlled
observations of real butterfly movement. Similar conclusions were reached using a
ground-truth test track prepared with a field tape and compass and subsequently
measured 20 times using the same methodology as the butterfly tracking. Median
error in the ground-truth track was slightly higher than the field data, mostly between
20 and 30 cm, but even for the smallest ground-truth step (70 cm), this is still a
signal-to-noise ratio of 3:1, and for steps of 3mor more, the ratio is greater than 10:1.
Such small errors relative to the movements being measured make these inexpensive
units useful for measuring insect and other small animal movements on small to
intermediate scales with budgets orders of magnitude lower than survey-grade units
used in past studies. As an additional advantage, these units are simpler to operate,
and insect or other small animal trackways can be collected more quickly than either
survey-grade units or more traditional ruler/gird approaches.
- Keywords: Checkerspot butterflies, Euphydrays, Insect movement, Movement ecology, Animal tracking, Butterfly movement, Tracking methods
- Keywords: Checkerspot butterflies, Euphydrays, Insect movement, Movement ecology, Animal tracking, Butterfly movement, Tracking methods
- Keywords: Checkerspot butterflies, Euphydrays, Insect movement, Movement ecology, Animal tracking, Butterfly movement, Tracking methods
- Keywords: Checkerspot butterflies, Euphydrays, Insect movement, Movement ecology, Animal tracking, Butterfly movement, Tracking methods
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