Recently the transportation or traffic problems are getting heavier and many solutions are proposed. Usually, they are divided by two methods, GPS and INS. Global Positioning System(GPS) is, using special 24 satellites, compute the receiver's position and at first, it was planned for the military usage. But in these years, GPS is also used in the navigation of the car, ship or plane. And the other navigation method is Dead Reckoning(DR). Building several sensors into the car and measure the varying angle and distance. It is a very simple theory to recognize the vehicle's position, but it has the fatal flaw that the temporary position errors are deposited and after a couple of minutes, that integrated error becomes heavier. In this thesis, the characteristics of GPS and DR are introduced and some methods to decrease the error of DR are proposed. And finally, a method to solve the problem of GPS that when the satellites are not visible, GPS is useless is suggested. Checking the number of the tracking satellite, make decision which navigation method is appropriate.
