Alpine Navigation Radio Owner's Manual download pdf (Page 15)

13-EN

Getting Started

Navigation systems

This navigation system uses three different sensing devices to determine

the present location and to track the progress of the vehicle. These three

devices are: a GPS (Global Positioning System) receiver which receives

digital signals from GPS satellites to determine the current position of

the vehicle, a gyroscope which determines which direction the vehicle

turns, and a speedometer pulse sensor which determine how far the

vehicle has travelled. Because this system incorporates a gyroscope and

a speed sensor, the system will be able to display the vehicle’s position

and track the vehicle’s progress even in areas where the GPS signal may

be blocked.

All map data is contained on a removable SD memory card. This system

integrates this unique map database with the sensing devices to

automatically plot out a route when a destination is entered. While

driving, the navigation system guides you along the route with pictorial

displays and verbal prompts.

• Altitude display accuracy can vary widely since the system uses only

GPS signals for determining altitude approximations. Unlike altitude

measurement, map matching accuracy is much more precise due to

calculation methods that utilize three inputs: 1) GPS signals, 2)

vehicle speed signals, and 3) the system’s built-in electronic gyro

signals.

This system receives signals from 3 or more GPS satellites (operated by

the United States Department of Defense) orbiting at an altitude of

21,000 kilometers and measures the present car position using the same

principles as triangulation. If the system receives signals from more

than three GPS satellites, positioning becomes possible.

The GPS positioning system uses both three dimensional and two

dimensional positioning.

Three dimension positioning

If GPS satellite reception is good, the positioning can be performed in

three dimensions: latitude/longitude/altitude.

Two dimension positioning

When GPS satellite reception is less than optimal positioning is

performed in two dimensions: latitude/longitude. In the latter case, since

altitude cannot be determined, minor positioning discrepancies can

occur three dimension positioning.

There may be a delay before the actual vehicle’s position

is displayed

Determination of the present vehicle’s position starts when the ignition

key is turned to the ACC or ON position, and ends when the key is

turned OFF. When the key is first turned to the ACC or ON position

delay of approximately one to two minutes is typical before the present

vehicle’s position can be displayed.

The error from the actual position of the vehicle

When GPS signals can be received from 4 or more satellites, 3

dimensional positioning (altitude, latitude, and longitude) of the vehicle

can be determined. In this case, error is in the range of 30 to 200 meters.

When GPS signals can only be received from 3 satellites, only two

dimensional positioning (latitude and longitude) can be determined,

resulting in a slight increase in error. When GPS signals can only be

received from less than three satellites, positioning of the vehicle

through GPS is not possible. In addition to the inherent GPS error

margin, the error rate may also increase if the United States Department

of Defense deliberately changes its accuracy.

Locations where GPS signals are received easily

The optimum locations for receiving GPS signals are locations that

command a good view where there are no tall buildings, trees, or other

objects to obstruct the signals.

The gyroscope is a sensor that accurately measures the angle by which

the direction of a vehicle or other moving body changes.

Gyroscopes are used in inertial navigation systems for airliners and

ships. In this navigation system, the gyroscope is used together with the

speed sensor, making it possible to display the position of the vehicle

even in locations where GPS signals may be blocked.

Preface

GPS (Global Positioning System)

Gyroscope/ Speed sensor

Direction Mileage

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Alpine Navigation Radio Owner's Manual Page 15

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