Dead Reckoning; How Do Gps And Dead Reckoning Work Together - Pioneer AVIC-505 Owner's Manual

Dead reckoning

What is dead reckoning?
Unlike GPS, dead reckoning relies on sensors installed in your vehicle to gather data about your
movements. The built-in gyrosensor is able to detect the turning motion of your vehicle, and
combines this with distance information taken from speed pulse data, as used by the
speedometer, to approximately track your position.
• The speed pulse data comes from the speed sensing circuit. The location of this speed sensing circuit
depends on your vehicle model. In some cases, it is impossible to make a connection to it, and in such
a case we recommend that the ND-PG1 speed pulse generator (sold separately) be used.

How do GPS and dead reckoning work together?

For maximum accuracy, your navigation system continually compares GPS data with your
estimated position as calculated from the gyroscopic data. However, if nothing but gyroscopic
data is available for a long period, positioning errors are gradually compounded until the
estimate of your location becomes unreliable. For this reason, whenever GPS signals are
available, they are matched with the gyroscopic data and used to correct it for improved
accuracy.
Learning function for better accuracy
To ensure maximum accuracy, the dead reckoning system incorporates a learning function. By
comparing the position it estimates with your actual position as obtained using GPS, it is able
to correct for various types of error, such as tyre wear and the rolling motion of your vehicle.
As you drive, it gradually builds up more data, or learning, and the accuracy of its estimates
gradually increases; as a result, you can expect your position as shown on the map to show
fewer errors after you have driven some distance.