Preface; Navigation Systems - Alpine NVD-T334 Owner's Manual

Preface

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 the 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 DVD ROM.
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.
GPS (Global Positioning System)
Delay time before the present vehicle's
position can be displayed
Determination of the present vehicle's position starts
when the ignition key is turned to the ACC or ON
positions and ends when the key is turned OFF. When
the key is first turned to the ACC or ON positions, there
is a slight delay of approximately one to two minutes
before the present vehicle's position can be displayed.
This system receives signals from 3 or more GPS
satellites (operated by the United States Department of
Defence) orbiting at an altitude of 21,000 kilometres and
measures the present car position using the same
principles as triangulation.
6
-EN
The error from the actual position of the
vehicle
When GPS signals can be received from 4 or more satellites, 3
dimensional positioning (the altitude, latitude, and longitude) of
the vehicle can be determined. In this case, the error from the
actual position of the vehicle is in the range of 100 to 655 feet
(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 slightly increased
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 errors from GPS, the error
rate can also be increased if the United States Department of
Defense deliberately changes the accuracy rate.
Gyroscope
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.