Improving the accuracy of low-cost GPS measurements for remote sensing applications
Field work in remote sensing often requires that the absolute position of a point on the Earth's surface can be determined with an accuracy of better than 100 m, for example to locate a Ground Control Point or to identify the land cover at a point corresponding to a particular pixel in an image. This paper assesses the extent to which low-cost, hand-held GPS (Global Positioning System) receivers can be used for this purpose. The nominal accuracy of GPS is 100 m, meaning that a single position measurement should yield a result within 100 m of the true position at least 95% of the time. Here, we investigate the extent to which this performance can be improved upon. Two approaches are studied: averaging several measurements, and correcting the measurement at one receiver using the known error at another. The first approach involves an investigation of the temporal correlation properties of the errors in a measured position. The correlation time is shown to be about 4 min for the horizontal coordinates and about 11 min for the vertical coordinate. Simple models are derived to allow the accuracy of an average measurement to be estimated, and it is shown that accuracies of typically 15 m (horizontally) and 30 m (vertically) can be achieved from 30 min of observation. The second approach involves an investigation of the spatial correlation properties of the errors. It is shown that these are inadequate to provide any improvement in accuracy.
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Document Type: Research Article
Affiliations: Scott Polar Research Institute, University of Cambridge, Lensfield Road, Cambridge CB2 1ER, England, UK; e-mail: [email protected]
Publication date: March 20, 2001