Mercedes-Benz ML320. Manual — part 236



Left rear rpm sensor (L6/3) (model 168)

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Wheel speed sensor, left front (L6/1)

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Right front rpm sensor (L6/2) (model 208, 210)



Left front rpm sensor (L6/1) and right front rpm sensor (L6/2) (models 203, 209)

The evaluation of the wheel speed signals reveals the mileage covered.

The wheel speed signals of the not driven wheels are evaluated, since their slip between the roadway and tire

is lower, which results in a more accurate result when calculating the mileage.

Calculation of the vehicle orientation

The navigation computer calculates the direction in which the vehicle is traveling (compass direction) from the
data from the gyrosensor and the sequence of locations calculated with the aid of the global positioning system
(GPS). The difference in the calculated mileage and the mileage actually covered between 2 turn-off points is
used to automatically recalibrate the tire circumference (necessary due to tire wear).

Calculation of the direction of motion

The navigation processor recognizes the direction of motion (forward or reverse) from the reverse signal.

Calibration of tire circumference

As a matter of principle, the navigation system recalibrates itself while driving as described. However, this may
require driving a longer distance. After changing tires, manual recalibration should therefore be accomplished.
To do this, it is necessary to enter the tire size (e.g.:195/050/015)and possibly the following information:



new tires (tread depth > approx. 5 mm)

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used tires (tread depth < approx. 5 mm)

The entry can be done two different ways:



With aid of STAR DIAGNOSIS.

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By calling the "Navigation --> TIRE" menu at the radio (A2)

Errors due to vehicle movement with switched off ignition lead to an inaccurate basic location finding.

Rolling backwards without the reverse gear engaged is evaluated as forwards motion, and may lead to an error
in the location finding. Rolling with the ignition switched off or vehicle transportation also falsify map
matching.

The errors are, however, corrected automatically after a short time by the navigation processor after

receiving GPS data.

A special calibration drive by driving around a defined test path is not ever required.

2001 Mercedes-Benz ML320

1998-2005 ACCESSORIES & BODY, CAB Electrical System - Body - 163 Chassis

me

BASIC LOCATION FINDING, FUNCTION - GF82.61-P-3006GI

MODEL 163 as of 1.9.01 with CODE (522) Modular control system (MCS) radio USA with CODE (357)
Navigation system - additional unit with CODE (818b) Single CD player - additional unit with CODE
(491) U.S. version

Fig. 47: Identifying Basic Location Finding, Function

Basic location finding (dead reckoning)

Is the basic function of permanent location finding It is accomplished permanently by the navigation processor
when the ignition is switched on and is not dependent on the CD-ROM map.

The current position is stored after the ignition is switched off.

The following information is calculated with the aid of basic location finding :



Distance traveled



Direction of motion (forward or backward) and

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Direction in which vehicle is pointing

Basic location finding is accomplished approx. once per second .

Distance traveled

The navigation processor receives the signals output by the front right wheel speed sensor (L6/2) from the
traction system control module (N47) via discrete leads.

Evaluation of the wheel speed signals allows calculation of the distance traveled.

Direction of motion

Map-supported location
finding, function

GF82.61-P-3008C

2001 Mercedes-Benz ML320

1998-2005 ACCESSORIES & BODY, CAB Electrical System - Body - 163 Chassis

me

The navigation processor recognizes the direction of motion (forward or reverse) from the reverse signal.

Direction in which vehicle is pointing

From the data of the gyrosensor and the sequence of the locations calculated with GPS the navigation
processor the calculates the direction in which the vehicle is pointing (compass direction).

The difference between calculated and actual distance traveled between two turning points is used for automatic
recalibration of the tire circumference (required due to tire wear).

Location finding errors during basic location finding

Rolling backwards without the reverse gear engaged is evaluated as forward motion, and may lead to an error in
the location finding.

Rolling with the ignition switched off or vehicle transportation also falsify map matching.

In both cases the deviation is automatically corrected by the navigation processor after receiving GPS data .

Calibration

Wheel calibration is not required following tire change.

GLOBAL POSITIONING SYSTEM LOCATION FINDING, FUNCTION - GF82.61-P-3007C

MODEL 163, 168, 170, 203.0 /2 /7, 208, 209.3 /4, 210 with CODE (353) Audio 30 APS

Basic representation of the GPS location finding shown on model 210

Global positioning system
location finding, function

GF82.61-P-3007GI

Map-supported location
finding, function

GF82.61-P-3008GI

Guidance, function

GF82.61-P-3012GI

Radio and navigation
module, location/purpose/
design/function

GF82.61-P-4109GI

2001 Mercedes-Benz ML320

1998-2005 ACCESSORIES & BODY, CAB Electrical System - Body - 163 Chassis

me

Fig. 48: Identifying Global Positioning System Location Finding

General information

The global positioning system (GPS) is a location finding system established by the US Defense Department
and is satellite supported. It is toll-free and is available throughout the world. A lot of satellites are located on
different orbits. The GPS satellites constantly transmit time and position data. If data from at least 3 satellites is
received it is possible to calculate the position of the receiver.

GPS position finding is irreplaceable for journeys outside the digitized map area and after vehicle transport (e.g.
train or ferry journeys and towing). A new GPS location finding (after interruption of satellite reception) can
last several minutes (up to 20 minutes when first commissioning the equipment).

Function

The navigation processor that is integrated in the radio (A2) calculates the location of the vehicle and the
accuracy of positioning from the satellite signals received and amplified.

The following components can receive satellite data:

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Telephone and GPS roof antenna (A2/49) (model 163)

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GPS antenna (A2/49a2) (model 168, 208.3, 210)

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GPS rear antenna (A2/23a2) (model 170, 208.4)

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GPS antenna (A2/23) (model 203, 209)

The actual calculation is essentially based on the measurement of the travel times of the signals sent
synchronously by the various satellites. Here, an important prerequisite is that the satellite and receiver clocks
are synchronized .

For this purpose, the receiver has an automatic time correction feature which again is possible with the aid of
the satellite signals.

If the navigation processor determines that the basic location finding is less accurate than the GPS location
finding, the position currently calculated is corrected using GPS data.

2001 Mercedes-Benz ML320

1998-2005 ACCESSORIES & BODY, CAB Electrical System - Body - 163 Chassis

me