Differential GPS (DGPS) is to install a high-precision GPS receiver at a  location that is accurately determined to form a base station. The position  measurement error or pseudo-range measurement error is obtained by comparing the  position measured by the base station receiving the GPS satellite signal with  the known position of the station, and the error is broadcast to the surrounding  space as the correction value. The GPS user receiver near the base station  receives the correction signal from the base station and corrects its GPS  measurement value, thus greatly improving the positioning accuracy. Many GPS  device providers set up DGPS transmitters in some areas for free use by  customers with DGPS-enabled GPS receivers.

　　When choosing a GPS device, users should consider some physical factors  besides navigation performance. With the continuous development of navigation  technology, especially the appearance of the third generation of Sirf navigation  chip, GPS products have been further improved in navigation performance, so that  the new generation of GPS products have little difference in positioning and  navigation performance. In addition to looking at the product positioning and  navigation performance when buying products, we should also consider the size,  weight, display screen, waterproof, shockproof, dustproof performance, high  temperature resistance, power consumption and other physical indicators.

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