there are some drawbacks with GPS receivers. The accuracy of the GPS receiver’s calculated position depends on the strength and number of signals that it receives. The gps receiver will always collect data from as many satellites as it can, and will choose the best four according to angle and strength of signal from which to compute a position (see previous section on GPS accuracy). But obstacles such as buildings, mountains, and tree canopies can distort the signals and introduce error to the reading. Even more serious, user mistakes such …