GPS is generally 12 channels now, and 12 satellites can be received at the same time. Early models, such as Garmin 45C is 8 channels. The GPS receiver receives the signal of 3 satellites to output 2D (that is, 2D) data. Only the latitude and longitude, no height. If you receive more than 4 satellites, you can output 3D data, which can provide an altitude height. But because of the earth's own problems, it is not too standard to circle, so there are some errors in high data. Some GPS receivers now have built -in air pressure gauges, such as ETREX's Summit and Vista. These machines combine the final altitude according to the high data obtained by the two channels, which should be more accurate.

　　The first boot of the GPS receiver, or the last shutdown location of the last shutdown of more than 800km during the booting distance, because the storage store stored in the receiver is not right, so re -position the receiver.

　　The use of the GPS receiver is under the wide visible sky, so it cannot be used in the house. The accuracy of holding GPS is generally about 10 meters, which means that one road can see that walking on the left or right. The accuracy mainly depends on the signal receiving of the satellite, and the distribution of satellites with receiving signals in the sky. If the distribution of several satellites is relatively decentralized, the positioning accuracy provided by the GPS receiver will be relatively high.

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