Navigation Systems - Alpine NVE-N872A Hardware 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 (sold separately). 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.
Note: 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.
GPS (Global Positioning System)
There may be a delay before the
actual vehicle's position is dis-
played
Determination of the present vehicle's posi-
tion 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.
6
Preface
This system receives signals from 3 or more
GPS satellites (operated by the United States
Department of Defense) orbiting at an altitude
of 13,100 miles (21,000 kilometers) and
measures the present car position using the
same principles as triangulation.
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.