Navigation Basics Author: Huiban Sabin & Rosu Ciprian
Content table Introduction – Navigation systems Features & characteristics History Technology GPS & Satellite Positioning Gyroscope Dynamic navigation / TMCs Road database / Maps Route calculation Algorithms used in Navigation System architecture overview Integration with other functions / devices Controversy Navigation system – comfort / safety feature? Navigation - real life stories 2/ Navigation Basics
Introduction - Navigation systems 3/ Navigation Basics
Features and characteristics(1) Map display – GPS position 2 D / 3 D display & satellite view Landmarks & POI Selecting a location (city or street, full address or by zip code) Route calculations Using different criteria / constrains Simulation / fly over Guidance Visual & audio guidance advices Augmented guidance – HUD information Additional information ETA & RTT speed & heading (compass) Dynamic navigation – reacting on route deviations, TI, traffic flow 4 / Navigation Basics
Features and characteristics(2) 5 / Navigation Basics
History Global Navigation Satellite System (GNSS) is the standard generic term for satellite navigation systems that provide autonomous geo-spatial positioning with global coverage. Global Positioning System (GPS) – is such a system, the only one fully functional in the world. In 1978 the first experimental Block-I GPS satellite was launched. In 1983, after Soviet interceptor aircraft shot down the civilian airliner KAL 007 that strayed into prohibited airspace due to navigational errors, killing all 269 people on board, U. S. President Ronald Reagan announced that the GPS would be made available for civilian uses once it was completed. 1940 - LORAN and DECCA Navigator – terrestrial 1985 – already 10 satellites orbited Earth 1957 – The Russians lunch Sputnik 6 /Navigation Basics 1994 – already 24 satellites orbited Earth 1989 – the first modern satellite is lunched now – wide used Navigation systems
Technology - GPS & Satellite Positioning(1) 7 /Navigation Basics
Technology - GPS & Satellite Positioning(2) 8 /Navigation Basics
Technology - Gyroscope A gyroscope is a device for measuring or maintaining orientation, based on the principles of angular momentum. Gyroscope is important for navigation systems when driving in areas with no GPS signal. In the near future a connection with the car’s mechanics will provide these kind of info, so the gyro will not be used anymore in car navigation systems. 9/ Navigation Basics
Technology - Dynamic navigation / TMCs Traffic Message Channel (TMC) is a standardized technology for delivering traffic and travel information to drivers. ADAS - Advanced Driver Assistance Systems – navigation system capable to analyze TMCs. It's typically digitally coded using the FM-RDS system on conventional FM radio broadcasts. Each traffic incident is sent as a TMC message. One message consists of an event code and a location code in addition to time details. The driver can choose to make a detour to avoid the reported incident. This information is centered and then sent to radio stations that can transmit them. The info generally coded in radio transmissions can vary from weather conditions, accident or other blockage / delay on route to more complex traffic flow display. TMCs are not supported in Romania for the moment. 10 / Navigation Basics
Technology - Road database / Maps The road database is a vector map of some area of interest. Street names or numbers and house numbers are encoded as geographic coordinates so that the user can find some desired destination by street address. There is no industry standard for satellite navigation maps. Map Formats CARi. N Database Format (CDF) S-Dal Map providers: Navteq Teleatlas 11 / Navigation Basics
Technology - Road database / Maps - CARin Map format CARi. N Database Format (CDF) is the format that is being used by Continental ( since 2007, when Siemens VDO was bought ) Vehicle manufacturers who have used or are still using this format in one or more of their ranges include: • Audi • BMW • Peugeot - 607 • Citroën - C 5 • Renault - pre October 2005 • Ford • Range Rover - pre August 2008 • Land Rover - pre August 2008 • Rolls-Royce • Mini • Rover - pre August 2008 • MG - pre October 2005 • SAAB • Nissan 12 / • Opel/Vauxhall - Vectra, Omega • Volkswagen Navigation Basics
Route calculation is the software component in a navigation system that determines the best route between two places according to the user’s preferences, traffic conditions, etc. Algorithms There are many algorithms used in personal navigation systems. Most are variations based on three algorithms: Dijkstra’s shortest path, BFS and A-Star for route calculation. Additional algorithms are used for searching a location (speller feature) or for rendering the map roads (Bezier curves). 13 / Navigation Basics
Algorithms used in Navigation - Dijkstra’s shortest path Dijkstra's algorithm works by visiting vertices in the graph starting with the object's starting point. It then repeatedly examines the closest not-yet-examined vertex, adding its vertices to the set of vertices to be examined. it expands outwards from the starting point until it reaches the goal. Dijkstra's algorithm is guaranteed to find a shortest path from the starting point to the goal, as long as none of the edges have a negative cost. Let's consider the concave obstacle as described in the second figure. Dijkstra's algorithm works harder but is guaranteed to find a shortest path. 14 / Navigation Basics
Algorithms used in Navigation - Best First Search (BFS) The Best-First-Search (BFS) algorithm works in a similar way, except that it has some estimate (called a heuristic) of how far from the goal any vertex is. Instead of selecting the vertex closest to the starting point, it selects the vertex closest to the goal. BFS is not guaranteed to find a shortest path. However, it runs much quicker than Dijkstra's algorithm because it uses the heuristic function to guide its way towards the goal very quickly. If we consider an concave obstacle, we can observe that the work load is lower that the previous algorithm, but the path found is not guarantied to be the shortest. 15 / Navigation Basics
Algorithms used in Navigation - A- Star Algorithm (A*) A* is like other graph-searching algorithms in that it can potentially search a huge area of the map. It's like Dijkstra's algorithm in that it can be used to find a shortest path. It's like BFS in that it can use a heuristic to guide itself. In the simple case, it is as fast as BFS. The secret to its success is that it combines the pieces of information that Dijkstra's algorithm uses (favoring vertices that are close to the starting point) and information that BFS uses (favoring vertices that are close to the goal). When talking about A*, g(n) represents the cost of the path from the starting point to any vertex n, and h(n) represents the heuristic estimated cost from vertex n to the goal. In the above diagrams, the yellow (h) represents vertices far from the goal and teal (g) represents vertices far from the starting point. A* balances the two as it moves from the starting point to the goal. Each time through the main loop, it examines the vertex n that has the lowest f(n) = g(n) + h(n). 16 / Navigation Basics
Algorithms used in Navigation - Interaction with the Map Database In order to use these algorithms you need a suitable map database. The road network needs to be described as a set of connected links, and, for each link, a "cost" needs to be assigned for traversing the link. This is one of the key features that distinguishes a map database as being a navigable map database rather than a database that can only be used for map display. Nodes 17 / Navigation Basics Segments
Algorithms used in Navigation - Speed-up Calculation There are many tricks and optimizations for speeding up the time taken to calculate a route between two places. Functional class attribute is a number that indicates how important a link is with regard to its use as a thoroughfare for traffic. A functional class 1 link is a stretch of road that is used for major inter-town links. In contrast, a functional class 5 link is one that you might expect to find in a residential back street. Implementations of the route calculation algorithms separate the road network according to the functional class attribute. The route calculation algorithms can be modified to start calculating routes from start to destination and destination back to start at the same time. When the two processes meet in the middle, the job is done! 18 / Navigation Basics
System architecture overview HMI Nav. BL Nav. Core 19 / Navigation Basics • Display data received from Nav. BL • Receive user input • Process data received from Nav. Core • Additional business logic • Access to DB and render map • Route calculation • Guidance handling
Integration with other functions/devices GPS receiver For receiving GPS data form satellites Radio For receiving TMC’s Car mechanics (steering wheel, speedometer) For assuring accurate positioning when no GPS info is available. Wireless connection For map / software update. Exchange info with other cars Audio system For playing guidance announcements 20 / Navigation Basics
Controversy - Navigation system – comfort / safety feature? Why comfort? All kind of info – geo coordinates, road name, altitude, RTT, ETA … Information about POI’s – can encapsulate also movies and pictures. Direction to gas stations, fast food stores … Why safety? Map display –info about the road ahead (specially at night). Information about current weather condition ahead. Information about traffic events, speed limits, one way streets, ghost drivers. Some vehicle producers locked out many of the features when the vehicle is in motion. 21 / Navigation Basics
Controversy - GPS – real life stories Saved by his GPS: Brett Pownceby successfully fought a speeding ticket with his global positioning system. (he proved that he was travelling 21 km/h slower). February 21, 2006 (Reuters) -- Fiddling around with in-car satellite navigation systems is causing motorists to lose concentration on the road, according to a survey released today by Privilege Insurance in England. The new GPS technology, rather than helping motorists, could be even more distracting than trying to read a map at the wheel, it said. Drivers following satellite navigation systems through a village called Crackpot have been directed along a track at the edge of a 100 ft cliff. All these because a map DB error. 22 / Navigation Basics
The end. Questions Thank you for the attention! 23 / Navigation Basics
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