To accurately determine the three coordinates of the current position in space, the car must receive signals from at least four satellites.
If the car is moving, this information is constantly changing. The navigation system computer determines which satellites are in the field of view and calculates their relative positions. Using this information, the computer compensates for deviations in the position of the satellites, which increases the accuracy of the car's positioning.
The signals used by the GPS system are called precise positioning signals (Precision positioning signal - PPS).
Positioning accuracy of PPS system:
- 22 meters in horizontal plane
- 27.7 meters in height
- The time measurement error is 200 nanoseconds
The navigation system receives information from satellites via a GPS antenna. Based on the GPS signals received from the satellites, the navigation system computer calculates the position of the vehicle. After the driver enters a destination, the navigation system computer calculates a route based on the driver's preset preferences or the default settings stored in the computer.
The navigation system receives GPS (Global Positioning System) information from satellites via a GPS antenna. Based on the GPS signals received from the satellites, the navigation system computer calculates the position of the vehicle. After the driver enters the desired destination, the navigation system computer calculates the route based on the driver's preset preferences or the default settings stored in the computer.
The navigation system is activated by pressing a soft key on the touch screen.
Navigation mode is initiated when the driver enters a destination. This can be done in the following ways:
- Entering an address using the touch screen.
- Entering postal code.
- Select previous destination.
- Selecting a location of interest from the map disk database.
- Selecting a starting point.
- Select a location stored in memory.
After the driver enters the destination, the system suggests the route to the driver by "scrolling" the map of the area on the screen and giving voice instructions. The shape and scale of the map output on the screen can be changed.
In addition to the navigation system, there are two other systems that provide additional information to the navigation system and the driver. Namely:
- Traffic Management Channel (TMC) - Europe only.
- Roadside Infrared and Radio Message System (VICS) - Japan only.
Traffic Message Channel (TMC)
Traffic Message Channel (TMC) data is now broadcast in many European countries.
TMC is a function of the Radio Data System (RDS), which operates in the FM (frequency modulation) band. The system transmits real-time traffic and weather information. TMC information is received using a regular FM antenna.
The data is received and decoded by the TMC receiver and sent to the navigation system, which forwards it further via its interface. TMC messages can be filtered in the navigation system computer, so that only messages relevant to the current trip are displayed. This allows the navigation system to adjust the route in time and offer the driver an alternative route to avoid trouble. The map displays all TMC events, not just those related to the plotted route.
TMC traffic information systems comply with international standards adopted by:
- organizations involved in collecting road data
- information service providers
- radio broadcasting companies
- car/receiver manufacturers
All TMC radios use a common list of event codes, but local databases (on the road map disc) may additionally contain country-specific codes for strategic European roads.
Roadside Infrared and Radio Message System (VICS)
A system for receiving messages from infrared and radio transmitters installed along the road (VICS) is in operation in Japan.
The VICS system transmits information to the navigation computer, which allows the driver of the vehicle to be informed about the traffic situation in the area and, if necessary, to calculate alternative routes. Information is transmitted to the navigation system via three channels:
1. Transmissions in the RF range
Radio frequency transmission is usually carried out from transmitters ("radio beacons") installed along roads, mainly on highways. Information is transmitted as follows:
- Traffic density
- Travel time to the next intersection
- Traffic conditions in adjacent areas and the possibility of exiting the motorway
- Road accidents
- Speed Limit
- Rules for changing lanes
- Tire Replacement Points
- Parking admissibility and availability of parking areas on motorways
2. Transmission in the infrared range.
The data transmitted in the infrared range is received by the infrared antenna located at the top of the instrument panel. The transmissions via the infrared channel are transmitted by radio beacons installed along the main roads. The following information is transmitted:
- Traffic density and travel time
- Road accidents
- Accidents
- Traffic restrictions due to road works
- Parking possibility
3. Transmissions in the FM range (frequency modulation).
FM (frequency modulation) broadcasts are received by an FM antenna; broadcasting is carried out within the RDS system in the FM range.
The following information is transmitted:
- Traffic density and travel time (covers a large area)
- Road accidents, road works, speed limits, lane changing rules (covers a large area)
- Parking availability information
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