1、 Automotive navigation system An automotive avigation system is a satellite navigation system designed for use in automobiles. It typically uses a GPS navigation device to acquire position data to locate the user on a road in the units map database. Using the road database, the unit can give directi
2、ons to other locations along roads also in its database. Dead reckoning using distance data from sensors attached to the drivetrain, a gyroscope and an accelerometer can be used for greater reliability, as GPS signal loss and/or multipath can occur due to urban canyons or tunnels. Some sorts can be
3、taken out of the car and used hand-held while walking. History Automotive navigation systems were the subject of extensive experimentation, including some efforts to reach mass markets, prior to the availability of commercialGPS. Most major technologies required for modern automobile navigation were
4、 already established when the microprocessor emerged in the 1970s to support their integration and enhancement by computer software. These technologies subsequently underwent extensive refinement, and a variety of system architectures had been explored by the time practical systems reached the marke
5、t in the late 1980s. Among the other enhancements of the 1980s was the development of color displays for digital maps and of CD-ROMs for digital map storage. However, there is some question about who made the first commercially available automotive navigation system. There seems to be little room fo
6、r doubt that Etak was first to make available a digital system that used map-matching to improve on dead reckoning instrumentation. Etaks systems, which accessed digital map information stored on standard cassette tapes, arguably made car navigation systems practical for the first time.2 However, Ja
7、panese efforts on both digital and analog systems predate Etaks founding. Steven Lobbezoo developed the first commercially available satellite navigation system for cars. It was produced in Berlin from start 1984 to January 1986. Publicly presented first at the Hannover fair in 1985 in Germany, the
8、system was shown in operation on the evening news from the first German television channel in that year. It used a modified IBM PC, a large disc for map data and a flat screen, built into the glove compartment. It was called Homer Alpine claims to have created the first automotive navigation system
9、in 1981. However, according to the companys own historical timeline,3 the company claims to have co-developed an analog automotive navigation product called the Electro Gyrocator, working with Honda. This engineering effort was abandoned in 1985. Although there are reports of the Electro Gyrocator b
10、eing offered as a dealer option on the Honda Accord in 1981, its not clear whether an actual product was released, whether any customers took delivery of an Electro Gyrocator-equipped Accord, or even whether the unit appeared in any dealer showrooms； Hondas own official history appears to pronounce
11、the Electro Gyrocator as not practical. Honda claims4 to have created the first navigation system starting in 1983, and culminating with general availability in the 1990 Acura Legend. The original analogElectro Gyrocator system used an accelerometer to navigate using inertial navigation, as the GPS
12、system was not yet generally available. However, it appears from Hondas concessions in their own account of the Electro Gyrocator project that Etak actually trumped Hondas analog effort with a truly practical digital system, albeit one whose effective range of operation was limited by the availabili
13、ty of appropriately digitized street map data. Technology Visualization Navigation systems may (or may not) use a combination of any of the following: top view for the map top view for the map with the map rotating with the automobile (so that up on the map always corresponds to forward in the vehic
14、le) birds-eye view for the map or the next curve linear gauge for distance, which is redundant if a rotating map is used numbers for distance schematic pictograms voice prompts Road database Contents The road database is a vector map of some area of interest. Street names or numbers and house number
15、s are encoded as geographic coordinates so that the user can find some desired destination by street address . Points of interest will also be stored with their geographic coordinates. Point of interest specialties include speed cameras, fuel stations, publicparking, and parked here. Contents can be
16、 produced by the user base as their cars drive along existing streets and communicating via the internet, yielding a free and up-to-date map. Physical Storage Format The Physical Storage Format (PSF) initiative is an industry grouping of car manufacturers, navigation system suppliers and map data su
17、ppliers whose objective is the standardization of the data format used in car navigation systems, as well as allow a map update capability. Standardization would improve interoperability, specifically by allowing the same navigation maps to be used in navigation systems from 19 manufacturers. Compan
18、ies involved include BMW, Volkswagen, Daimler,Renault, ADIT, Aisin AW, Alpine Electronics, Navigon, Bosch, DENSO, Mitsubishi, Harman Becker, Panasonic, PTV, Continental AG, Clarion, Navteq, Tele Atlas and Zenrin. Media The road database may be stored in solid state read-only memory (ROM), optical me
19、dia (CD or DVD), solid state flash memory, magnetic media (hard disk), or a combination. A common scheme is to have a base map permanently stored in ROM that can be augmented with detailed information for a region the user is interested in. A ROM is always programmed at the factory； the other media
20、may be preprogrammed, downloaded from a CD or DVD via a computer or wireless connection (bluetooth, Wi-Fi), or directly used utilizing a card reader. Some navigation device makers provide free map updates for their customers. These updates are often obtained from the vendors website, which is accessed by connecting the navigation device to a PC.
