Lincoln Blackwood (2002) Navigation System [3/48] Introduction

HOW DOES THE NAVIGATION SYSTEM WORK?

The navigation system is a tool to assist the driver in daily traffic. The

system allows you to enter the destination and activate “Guidance”, and

the system provides guidance advice through both audio and visual

advice.

Determination of the vehicle position

The movement of the vehicle is measured by sensors which are

integrated into the navigation system. The distance driven is recorded by

an electronic signal from the speedometer and the rotary movements of

turns by the gyroscope (a rotary measurement system). The information

from these sensors is, however, not always exact as the values can be

affected by tire slippage, varying tire pressure due to changes in

temperature, etc.

Data from the sensors, in conjunction with positional information

received from the global positioning system is transmitted to the

navigation computer. The resultant calculated position is then compared

against the road network data stored on the CD-ROM in order to display

the current vehicle position.

GPS (global positioning system)

The global positioning system is based on the reception of navigation

signals from a total of 24 GPS satellites at a height of 20 920 km

(13 000 miles).

Signals from at least four satellites must be received to determine the

vehicle position with sufficient accuracy. The GPS receiver can handle up

to eight satellite signals simultaneously. This allows an accuracy of

approximately 100 m (328 ft), which is further improved by other

sensors so that a final accuracy of approximately6mto18m

(20 ft to 60 ft) can be reached.

When the vehicle is parked for a long period of time, the satellites

change their orbital positions. Therefore, when the ignition is turned on

again it can take a few minutes before the navigation system can pick up

enough satellites and evaluate the received signals.

• Sufficient reception is indicated by the green symbol that appears in

the system’s display. If the satellite symbol remains red, the GPS

reception is not sufficient.

Introduction