Toyota Tundra. Manual — part 468

Fig. 6: Global Positioning System Flow Chart
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

NAVIGATION SYSTEM OPERATION DESCRIPTION CHART

Operation

Description

Vehicle

Position

Calculation

Navigation receiver calculates current vehicle position (direction and current
position) using direction deviation signal from gyro sensor and running
distance signal from vehicle speed sensor, and creates driving route.

2009 Toyota Tundra

2009 ACCESSORIES AND EQUIPMENT Navigation - Tundra

HINT:

The combination of autonomous and GPS navigation makes it possible to display the vehicle
position even when the vehicle is in places where the GPS radio wave cannot receive a
signal. When only autonomous navigation is used, the mapping accuracy may slightly
decline.

Fig. 7: Identifying Autonomous Navigation And GPS Navigation System
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

Map Display

Processing

Navigation receiver processes vehicle position data, vehicle running track,
and map data from map disc.

Map Matching

Map data from the map disc is compared to vehicle position and running
track data. Then, vehicle position is matched with nearest road.

GPS

Correction

Vehicle position is matched to position measured by GPS. Then,
measurement position data from GPS unit is compared with vehicle position
and running track data. If the position is very different, GPS measurement
position is used.

Distance

Correction

Running distance signal from vehicle speed sensor includes error caused by
tire wear and slippage between tires and road surface. Distance correction is
performed to account for this. Navigation receiver automatically offsets
running distance signal to make up for difference between it and distance
data of map. Offset is automatically updated.

2009 Toyota Tundra

2009 ACCESSORIES AND EQUIPMENT Navigation - Tundra

b. Autonomous navigation

This method determines the relative vehicle position based on the running track determined by the
gyro and vehicle speed sensors located in the navigation receiver.

1. Gyro sensor

Calculates the direction by detecting angular velocity. It is located in the navigation receiver.

2. Vehicle speed sensor

Used to calculate the vehicle running distance.

c. GPS navigation (Satellite navigation) This method detects the absolute vehicle position using radio

waves from a GPS satellite*.

HINT:

*: GPS satellites were launched by the U.S. Department of Defense for military purposes.

Fig. 8: Identifying GPS Navigation (Satellite Navigation)
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

SATELLITES SPECIFICATION

2009 Toyota Tundra

2009 ACCESSORIES AND EQUIPMENT Navigation - Tundra

d. Map matching

The current driving route is calculated by autonomous navigation (according to the gyro sensor and
vehicle speed sensor) and GPS navigation. This information is then compared with possible road
shapes from the map data in the map disc and the vehicle position is set onto the most appropriate
road.

Fig. 9: Identifying Map Matching
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

Number of

satellites

Measurement

Description

2 or less

Measurement
impossible

Vehicle position cannot be obtained because number of
satellites is not enough.

3

2-dimensional
measurement is possible

Vehicle position is obtained based on current longitude
and latitude (this is less precise than 3-dimensional
measurement).

4

3-dimensional
measurement is possible

Vehicle position is obtained based on current longitude,
latitude and altitude.

2009 Toyota Tundra

2009 ACCESSORIES AND EQUIPMENT Navigation - Tundra