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SEL683V
System Description
=NAEL0421
OUTLINE
NAEL0421S01
The Navigation System (Multi-AV System) relies upon three sens-
ing devices in order to determine vehicle location at regular time
intervals.
1. Vehicle speed sensor: Determines the distance the vehicle has
traveled.
2. Gyro (Angular velocity sensor): Determines vehicle steering
angle and directional change.
3. GPS antenna (GPS data): Determines vehicle forward move-
ment and direction.
The data provided by the three sensing functions together with a
comparison of the mapping information read from the CD-ROM
drive permit accurate determination of the vehicle’s current location
and subsequent course (map matching). The information appears
on a liquid crystal display.
This comparison of GPS data (vehicle position sensing) and map
matching permits precise determination of vehicle location.
SEL684V
Position Sensor Operating Principles
NAEL0421S0101
The sensor determines current vehicle location by calculating the
previously sensed position, the distance traveled from this position,
and the directional changes occurring during this travel.
1. Distance traveled
The distance traveled is calculated using signals received from
the vehicle speed sensor. The sensor automatically compen-
sates for the slightly reduced wheel and tire diameter resulting
from tire wear.
2. Forward movement (Direction)
Changes in the direction of forward movement are calculated
by the gyro (angular velocity sensor) and the GPS antenna
(GPS data). Each of these functions has its advantage and
disadvantages. Depending upon conditions, one function takes
precedence over the other to accurately determine the direc-
tion of forward movement.
Function type Advantage Disadvantage
Gyro (Angular
velocity sen-
sor)
I Able to accurately detect
minute changes in steering
angle and direction.
I Calculation errors may
accumulate over a long
period of continuous
vehicle travel.
GPS antenna
(GPS data)
I Able to sense vehicle travel
in four general directions
(North, South, East, and
West)
I Unable to detect direction
of vehicle travel at low
vehicle speeds.
NAVIGATION SYSTEM
System Description
EL-406
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