Mercedes-Benz ML320. Manual — part 237

In addition, the vehicle's course of travel is determined with the aid of the sequence of the locations calculated
with GPS.

Possible interference when receiving GPS signals

Since GPS operates in the GHz range (microwaves) and the signals are weak, reception interference can occur
as the result of:



atmospheric interference, e.g. weather, water vapor, fog



multiple reception resulting from reflecting of signals, e.g. from building walls



Signal shadows, e.g., in built-up areas, tunnel, in the proximity of higher buildings and trees

GPS reception therefore necessitates a clear view of the sky. The location finding accuracy of the GPS system is
100 m or better.

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

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. 49: Identifying Global Positioning System Location Finding

General

The global positioning system (GPS) is a satellite-supported location finding system. It is not subject to fees

GPS/CTEL roof antenna
location/task/design/ function

Models 163,
168,208.3,210

GF82.70-P-4111A

Global positioning system antenna,
location/ task/design/function

Models 170, 208.4

GF82.61-P-4106A

Models 203, 209.3

GF82.61-P-4106E

Model 209.4

GF82.61-P-4107Q

Antenna splitter,
location/task/design/function

Model Series 163

GF82.85-P-3107B

2001 Mercedes-Benz ML320

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

me

and is available worldwide . Presently there are 266 satellites on 6 different earth orbits. The GPS satellites
permanently transmit time and position data. If data from a minimum of 3 satellites is received (with two-
dimensional location finding) it is possible to calculate the position of the receiver.

The GPS location finding is particularly important when driving outside of the digitized map area and
following vehicle transport (e.g. train, ferry or towing).

A repeated GPS location finding (following satellite reception interruption) can take several minutes (when
unit is initially started up to 20 min .).

GPS map matching function

The navigation processor calculates the location of the vehicle and the accuracy of positioning from the
satellite signals received and amplified by the GPS antenna (A2/49) . The current calculation is based
primarily on the measurement of the transmission times for the signals transmitted 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 precise than the
GPS location finding, the currently calculated position is corrected with the aid of the GPS data .

Moreover, the vehicle route is determined from the location sequence calculated with GPS .

Approx. 50 new GPS location finding calculations are performed each minute.

Possible interference when receiving GPS signals

Since GPS operates in the GHz (microwave) range and the signals are weak, reception interferences can
occur from



atmospheric interferences, e.g. weather, water vapor, fog,



multiple path reception due to signal reflections, e.g. from building walls



Signal shadows, e.g. in built-up areas, tunnels, high buildings, trees

A free view of the sky is therefore necessary for GPS reception The location finding accuracy is approx. 100
m or better .

Basic location finding,
function

GF82.61-P-3006GI

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

GPS roof antenna/telephone,

GF82.70-P-4111A

2001 Mercedes-Benz ML320

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

me

MAP-SUPPORTED LOCATION FINDING, FUNCTION - GF82.61-P-3008C

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

Basic representation of the map-supported location finding shown on model 210

Map-supported location finding (map matching) is available only in the digitized area of the DVD map.

A deviation can be recognized and corrected automatically by comparing the calculated position of the vehicle
with the possible positions on the DVD map.

Fig. 50: Identifying Map-Supported Location Finding Function

Function

The position of the vehicle is continuously followed on the DVD map by the navigation processor. A number of
alternative routes are calculated preliminarily in the digitized area of the DVD map. If the route driven varies
from one of the possible routes, the position coordinates for basic location finding are corrected where
necessary.

The navigation processor is integrated in the radio (A2).

Loading the DVD map data

The navigation processor has a read/write memory (RAM) for storing the DVD map data. However, this
memory is not large enough to store the entire DVD map (currently approx. 10 %). For this reason, the
navigation processor loads into the memory only the map data required for route guidance.

Here, different storage methods are used depending on whether the destination is in the near vicinity of the
vehicle or further away:

The following methods are used to store the data:

location/purpose/
design/function

2001 Mercedes-Benz ML320

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

me



If the destination is in the near vicinity, a map area is loaded within a radius of approx. 100 km of the
vehicle location ("Local area").



For destinations further away, an area is selected surrounding the vehicle location, the destination and the
concrete route to the destination ("Corridor formation").

After storing the map data, the DVD with the map data can be taken out of the drive. Now, audio CDs can also
be played.

If the driver deviates too far from the calculated route during the course of navigation system and thereby leaves
the map area stored in the navigation processor, it may be necessary to insert the DVD again in order to
calculate a new route. The navigation processor requests this automatically.

Location errors

The errors are classified into 2 categories:



Incorrect position indication between 2 driving instructions (may not occur more than once every 500
km)



Incorrect driving instruction (may not occur more than once every 1,000 km)

MAP-SUPPORTED LOCATION FINDING, FUNCTION - GF82.61-P-3008GI

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

General

Map-supported location finding is available only in the digitized area of the CD-ROM map.

By comparing the calculated vehicle position with the CD-ROM map it is possible to recognize and
automatically correct the deviation.

Function

The vehicle position is permanently followed by the navigation processor on the CD-ROM map. If the route
deviates from the calculated route the position coordinates of the basic location finding are corrected if
necessary.

Global positioning
system location finding,
function

GF82.61-P-3007C

2001 Mercedes-Benz ML320

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

me