Mapping Stream Habitats with a Global Positioning System: Accuracy,Precision, and Comparison with Traditional Methods |
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Authors: | Email author" target="_blank">Daniel?C?DauwalterEmail author William?L?Fisher Kevin?C?Belt |
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Institution: | (1) Oklahoma Cooperative Fish and Wildlife Research Unit, Department of Zoology, Oklahoma State University, Stillwater, Oklahoma 74078, USA;(2) US Geological Survey, Oklahoma Cooperative Fish and Wildlife Research Unit, Department of Zoology, Oklahoma State University, Stillwater, Oklahoma 74078, USA;(3) Oklahoma Cooperative Fish and Wildlife Research Unit, Department of Zoology, Oklahoma State University, Stillwater, Oklahoma 74078, USA |
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Abstract: | We tested the precision and accuracy of the Trimble GeoXT™ global positioning system (GPS) handheld receiver on point and
area features and compared estimates of stream habitat dimensions (e.g., lengths and areas of riffles and pools) that were
made in three different Oklahoma streams using the GPS receiver and a tape measure. The precision of differentially corrected
GPS (DGPS) points was not affected by the number of GPS position fixes (i.e., geographic location estimates) averaged per
DGPS point. Horizontal error of points ranged from 0.03 to 2.77 m and did not differ with the number of position fixes per
point. The error of area measurements ranged from 0.1% to 110.1% but decreased as the area increased. Again, error was independent
of the number of position fixes averaged per polygon corner. The estimates of habitat lengths, widths, and areas did not differ
when measured using two methods of data collection (GPS and a tape measure), nor did the differences among methods change
at three stream sites with contrasting morphologies. Measuring features with a GPS receiver was up to 3.3 times faster on
average than using a tape measure, although signal interference from high streambanks or overhanging vegetation occasionally
limited satellite signal availability and prolonged measurements with a GPS receiver. There were also no differences in precision
of habitat dimensions when mapped using a continuous versus a position fix average GPS data collection method. Despite there
being some disadvantages to using the GPS in stream habitat studies, measuring stream habitats with a GPS resulted in spatially
referenced data that allowed the assessment of relative habitat position and changes in habitats over time, and was often
faster than using a tape measure. For most spatial scales of interest, the precision and accuracy of DGPS data are adequate
and have logistical advantages when compared to traditional methods of measurement. |
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Keywords: | Stream habitat GPS GIS Positional error Spatial data |
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