Now various countries’ big city all has the traffic congestion problem. Take the US as the example, 1980~2003 year period, year number of vehicles by 77% speed rise, but the same time path construction course’s growth number is actually only 2%, in municipal transportation’s peak time, 54% buses is at the crowded condition. As a result of traffic congestion, the people consumed every day at coming and going to work’s time compared to usually average many 1. 5 hours. Simultaneously caused the commercial vehicles to delay in the transportation, increased the transportation cost. But limited factor and so on land and economic resource restrictions, cause the path construction not to be impossible to achieve relative satisfaction the course number. Must want, in does not expand under the road network scale premise, enhances the existing traffic road network traveling capability, needs to synthesize the utilization advanced science and technology method to enhance the transportation the efficiency.
Plan choice
The intelligence transportation system (Intelligent Transportation System, ITS) is the advanced information technology, the data communication transmission technology, the electronic control technology, the sensor technology as well as the computer processing technology and so on synthesizes effectively utilizes in the entire transportation system, thus establishes one kind in the wide range, the omni-directional display function real-time, accurate, the highly effective transportation integrated management system. This system mainly includes the traffic control system, the journey requirements management system, the mass transit operation system, the vehicles run-time system, the electronic toll collection system, the emergency management system management system, the vehicles monitoring and the safety system and so on, it is the high tech and the advanced means of communication in transportation system’s conformity application.
The vehicles supervisory system is its important component. The nearly all vehicles supervisory system relies on GPS and the GIS electronic map technology. Under the GIS condition’s electronic map database has provided depositing and a management monitoring information visualization carrier for the vehicles supervisory system. The GPS localization technology causes in the vehicles monitoring real-time possibly to track into. The communication has built up a data communication bridge between GIS and GPS, causes long-distance possibly to monitor into. Through the accurate localization, the coordination communication as well as the electronic map, the vehicles supervisory system may carry on the real-time route monitoring, thus guides the vehicles to avoid jams the road section, sharpens the road capacity, the alleviation traffic congestion and the jamming. This article introduces is based on the GPS bus real time display and the positioning system.
System feasibility analysis
In the 1990s, our country to alleviate the transportation effectively the tense pressure, has introduced the intelligent transportation idea, and took the measure to speed up the application intelligence transportation technology positively. At present, the domestic ITS core technologies’s research mainly concentrates in aspects and so on pattern recognition technology, transportation emulation technique, GPS/GIS localization navigation technology satellite, junction throughflow theory. The GPS application mainly manifests in the vehicles localization guidance, but the GPS vehicles supervisory system’s application is on the rise, especially on the special purpose vehicle, the rental car oneself starts to promote the application. For example, Beijing has completed the British SC001′HE Yugoslavia TRANSYT-7P transportation message control system’s introduction, the installment and the operational guidance research successfully; Shanghai has established the rental car union dispatch company, has established the entire profession GPS control center.
In our country’s transportation, GPS and the wireless communication technology unifies started widely to apply in cash truck’s warning, the localization monitoring, the police vehicle, the fire engine, ambulance’s command and adjustment. Some city’s rental car, rented a car professions and so on service, physical distribution allocation already to start using the GPS technology to carry on the monitoring track, the dispatch management to the vehicles, distributed the vehicles reasonably, by the quickest speed response user’s request, reduced the energy to consume, saves the run cost. In the vehicles guidance aspect, establishes the Computerized radio set through the GPS vehicles supervisory system in the city, the real-time issue transportation information, the vehicle carries the equipment through the GPS pinpointing, the bonding electron map and the real-time transportation information, the automatic match optimal choice, and realizes vehicles’ automatic navigation.
In summary, the GPS technology was quite already mature in the transportation system application, therefore, this system applies the GPS technology in our country’s bus’s real time display and the localization is feasible.
Key technologies
1 GPS dynamic localization
The GPS localization may divide into the static localization and the dynamic localization based on the undetermined state of motion. The generalized GPS dynamic localization is the GPS guidance, like uses in the land, aquatic and the aerospace movement carrier guidance. According to the application goal and accuracy requirement’s difference, the GPS dynamic localization method is also different. Mainly divides into the following several kinds: Simple point dynamic localization, real-time difference dynamic localization, post-processing difference dynamic localization.
What this system uses is the simple point dynamic localization method, carries the GPS terminal by the vehicle to obtain the mobile target independently the real-time position, and this positional information, through wireless communication system transmission to monitoring center, thus describes the mobile target in the monitoring center the path, realizes vehicles’ real-time monitoring and each kind of information gathering.
2 GIS in vehicles monitoring application
GIS is the collection survey science and technology, the data bank technology and the computer graphics technology in a body’s emerging edge discipline. In the vehicles monitoring domain’s application, GIS is one kind of collection city geographic information system and the thing sign subject information in a body face the vehicles guidance, the track information system, it may demonstrate that each kind of proportion the electronic map, can supply each kind of polling message reliably rapidly for the vehicles, chooses the vehicles road traffic during on-line any two nodes conveniently nimbly the best driving route, and carries on the real-time track, the dispatch management in the monitoring center to the vehicles. The GIS technology includes in the vehicles supervisory system’s major function: Provides the good presente in figures and diagrams man-machine contact surface, by the different mark demonstration state of roads information, reminds the pilot; On the vector electronic map, the user may carry on the random enlargement, the reduction, roaming, revolving, the lamination demonstration and so on; Can on the electronic map real-time, demonstrate accurately vehicles’ position, tracks vehicles’ travel process, and may playback vehicles’ movement path; The user may carry on the geography entity the inquiry; On the electronic map, the user may carry on the way plan, most short-path’s choice and so on.
in 3 vehicles supervisory system’s coordinate transformation
In the usual situation, the plane coordinate system’s conversion mode has the equiform transformation, the affine transformation, the bilinear transform as well as two and three multinomial transformations and so on. The equiform transformation is two place coordinates system’s transformation completely, has not considered the system error; The affine transformation has considered vertically and horizontally the coordinate scale factor difference in the equiform transformation foundation, but to eliminate and weaken the error which between two coordinate system’s translations, revolving, the reproduce by pantograph, the curvature of the earth as well as the Earth projected cause, generally needed two times or the higher mode equation establishes the mapping relations.
In the vehicles positioning system, use type 1) may satisfy the vehicles dynamic localization generally the request which transforms to the coordinate.
U=a0 a1x a2y (1)
V=b0 b1x b2y
4 based on serial port communication vehicles guidance data transmission
Realizes the serial port correspondence commonly used method using Delphi7.0 to have 3 kinds: First, the use controls, like MSCOMM controls, SPCOMM to control and Cport3. 0 control; Second, uses the API function; Third, transfers other serial port signal procedure. And is more complex using the API compilation serial port signal procedure, needs to master the massive correspondence knowledge. Comparatively speaking, controls using Cport3.0 relatively to be simple, and should control to have rich with the serial port correspondence close related attribute and the event, has provided to serial port each kind of operation, easy to realize.
5 GSM short delays of information to locator data influence
Although the GSM short information service can transmit the vehicles localization information reliably, but because the short information technology’s limit as well as the channel crowded degree’s difference, causes the locator data the transmission to have the varying degree the detention.
The experiment indicated: When short information by biggest byte transmission, the unidirectional transmission latency is the 5s accumulation probability distribution may achieve 92. 80%, regarding the low speed mobile termination, such detention base wooden achieves the monitoring, the guidance application request. But regarding the high speed movement’s vehicle, the 3~5s detention possibly too steadily, for example, the speed was 120 kilometers automobiles, 5s already drove out of 167m, when the locator data passed to the monitoring center oneself had the 167m error’s accumulation, if this kind of error distributed in the street spreads across, the street intersection spread all over in the city, will cause it to sell at a discount greatly as the policy-making reference confidence.
From the mobile termination reduction latency’s main method reduces the data quantity size which a time transmits, if reduces time data transmission capacity to 70 bytes, then calculates theoretically the transmission latency is 1.9s. Further reduced data quantity also will reduce the transmission latency. We when use the NMEA-0183 form transmits the GPS localization guidance data, first to the data carries on processing, only the longitude, the latitude and the time makes into the short note data packet, causes the data packet to be as far as possible short, reduces the short note transmission the latency. Moreover, may carry on the dead-reckoning to the vehicles, causes to monitor vehicles’ real-time precision to further enhance.
System estimate
This article unified GPS, GIS as well as the computer data technology and the modern data communication technology has conducted the vehicles supervisory system’s research, developed one to have all-weather satellite positioning, the electronic map demonstration and the vehicles real-time monitoring function GPS vehicles supervisory system initially.
