Pioneer AVIC-Z1 operation manual How do GPS and dead reckon- ing work together?, Map matching

NAVI/AV

Appendix

The method of positioning changes as follows depending on whether the speed pulse of your vehicle is detected or not:

3D hybrid mode

This is active when the speed pulse is detected. Inclination of a street can be detected.

Simple hybrid mode

When the speed pulse is not detected, position- ing is performed in this mode. Only horizontal movement is detected, so it becomes less accu- rate. Also, when the positioning by GPS is not available, such as when your vehicle enters a long tunnel, the discrepancy between your actual and calculated position may become bigger.

❒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 reckon- ing work together?

For maximum accuracy, your navigation system continually compares GPS data with your esti- mated position as calculated from the data of 3D Hybrid Sensor. However, if only the data from the 3D Hybrid Sensor is available for a long period, positioning errors are gradually compounded until the estimated position becomes unreliable. For this reason, whenever GPS signals are avail- able, they are matched with the data of the 3D Hybrid Sensor and used to correct it for improved accuracy.

To ensure maximum accuracy, the dead reckon- ing system learns with experience. By comparing the position it estimates with your actual position as obtained using GPS, it can correct for various types of error, such as tire wear and the rolling motion of your vehicle. As you drive, the dead reckoning system gradually gathers more data, learns more, and the accuracy of its estimates gradually increases. So, after you have driven some distance, you can expect your position as shown on the map to show fewer errors.

❒If you use chains on your wheels for winter driving or put on the spare wheel, errors may suddenly increase because of difference in wheel diameter. The system detects the fact that the tire diameter has changed, and auto- matically replaces the value for calculating distance.

❒If the ND-PG1 is used or if your vehicle is oper- ating in Simple hybrid mode, the distance cal- culation value cannot be replaced automatically.

Map matching

As mentioned, the GPS and dead reckoning sys- tems used by this navigation system are suscepti- ble to certain errors. Their calculations may, on occasion, place you in a location on the map where no road exists. In this situation, the pro- cessing system understands that vehicles travel only on roads, and can correct your position by adjusting it to a nearby road. This is called map matching.

With map matching

Without map matching

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