GPS (Global Positioning System)

WARNING: This page is about a different car, the 2009 Nissan Murano. However, it is still accessible from the selected car via links, so may be relevant.

GPS (Global Positioning System) is developed for and is controlled by the US Department of Defense. The system utilizes GPS satellites (NAVSTAR), transmitting out radio waves while flying on an orbit around the earth at an altitude of approximately 21,000 km.

The receiver calculates the travel position in three dimensions (latitude/longitude/altitude) according to the time lag of the radio waves that four or more GPS satellites transmit (three-dimensional positioning). The GPS receiver calculates the travel position in two dimensions (latitude/longitude) with the previous altitude data if the GPS receiver receives only three radio waves (two-dimensional positioning). GPS position correction is not performed while the vehicle is stopped.

Fig 1: Identifying GPS (Global Positioning System)

Courtesy of NISSAN MOTOR CO., U.S.A.

Accuracy of GPS will deteriorate under the following conditions:

In two-dimensional positioning, GPS accuracy will deteriorate when altitude of the vehicle position changes.
The position of GPS satellite affects GPS detection precision. The position detection may not be precisely performed.
The position detection is not performed if GPS receiver does not receive radio waves from GPS satellites. (Inside a tunnel, parking in a building, under an elevated highway etc.) GPS receiver may not receive radio waves from GPS satellites if any object is placed on the GPS antenna.

NOTE:

The detection result has an error of approximately 10 m even with a high-precision three dimensional positioning.
There may be cases when the accuracy is lowered and radio waves are stopped intentionally because the GPS satellite signal is controlled by the US trace control center.