Location of moving objects based on satellite navigation systems..
Petrov Nikolay Nikolaevich, Candidate of Technical Sciences
LOCATION OF MOBILE OBJECTS BASED ON SATELLITE NAVIGATION SYSTEMS
This article continues a series of articles devoted to positioning systems and their use to ensure the safety of mobile objects. The article examines positioning systems using satellite radio navigation methods. The material for the article was obtained on the basis of information materials from manufacturers (technical descriptions, advertising brochures, etc.), so the depth and degree of detail directly depend on how detailed the materials were presented. The author apologizes in advance to those legal entities and individuals who find the description of their products not entirely accurate, and is ready for any form of cooperation with them to restore the truth. The author is also far from thinking that this article examines all the systems currently available on the market.
As noted in the first article of this series, satellite navigation system equipment is high-tech and can be easily integrated with other types of hardware and software. This allows even small firms with experience in mobile communications equipment and geoinformation software for personal computers to undertake the creation of vehicle dispatch monitoring systems, achieving a certain degree of commercial success. In the simplest case, the structure of such a system looks like this:
- a navigation receiver operating on signals from the GPS NAVSTAR SRNS is installed on the vehicle (as OEM equipment, this receiver costs $150-300), which is connected via the RS232 interface to an amateur packet radio modem of the TNC-2 standard (up to $200). The modem is connected via the audio interface to an arbitrary VHF car radio station (up to $400) operating in Conventional Radio mode;
- a personal computer is operating in the control center, on which the MapInfo GIS package, a scanned raster map, and an application written in MapBasic are installed, providing visualization of the current location of a moving object against the background of the map;
- a radio modem (similar to the one installed on board) and a radio station with an antenna are connected to the control computer.
Despite the apparent simplicity, such systems can perform their functions quite effectively in some cases. However, such a system has some significant limitations that prevent it from being used for serious applications. Firstly, this is the inefficient use of the radio frequency spectrum (Conventional Radio mode on dedicated frequencies, “overload of the AX25 protocol used in packet radio modems, implementation of error protection only by re-querying, low data transfer rate due to the use of the voice channel band and, as a consequence of all this, low system throughput). Secondly, the complexity of organizing radio coverage of a large territory. The transmission mode through repeaters with repetition (digipeaters) provided by the AX25 protocol can work effectively only along long routes. Thirdly, the complete vulnerability of the system to outside penetration — both for the purpose of intercepting data and for the purpose of unauthorized use of the data transmission network infrastructure. In reality, such a system can provide location control for 10–20 vehicles with an information update period of 1–5 minutes for each vehicle.
The projects presented below, completed at a professional level, usually provide the ability to work in various data transmission networks and allow the implementation of real working systems of various levels of complexity both for small fleets of vehicles (several dozen) and for several thousand mobile objects.
The company PRIN, one of the oldest companies in the sector of positioning systems based on satellite navigation technologies, offers a wide range of equipment and software. The equipment is mainly produced by the company Trimble Navigation, which is the world leader in commercial navigation equipment. The software is also developed by Trimble, but PRIN also offers its own developments. Trimble's onboard equipment allows configuring systems of varying complexity. In the simplest case, a Placer-400 terminal is installed on a vehicle, including a navigation receiver and a simple radio modem for connecting to a radio station. A more complex PSC-200 unit includes a microcontroller that provides connection of a number of onboard sensors (ignition status sensor, discrete input lines, parallel interface), as well as additional motion sensors that allow determining the location of the vehicle based on dead reckoning methods in the absence of visibility of navigation satellites. The Echo XL information terminal can be connected to the PSC-200 controller, providing a visual interface for the driver with the dispatch system. The function keys provide transmission of several standard messages. A large screen with large, clear symbols and adjustable backlighting allows the driver to read the information transmitted from the dispatch center in any lighting. Pressing keys and receiving information messages are accompanied by sound signals.
A number of applications of varying complexity are also offered for the software of the systems in the monitoring center. For small transport fleets (up to 35 moving objects), the PC Vtrak package can be used. The AVL Manager package contains a full set of software tools for building a tracking system and operational control over a large transport fleet (up to 1000 vehicles). The system based on this package ensures registration of vehicles and controls access to the system. For each transport unit, up to 30 different types of messages are set, automatically issued when the vehicle status changes. Information messages from on-board equipment are distributed among different categories, messages containing information about emergency situations on board are grouped separately. To display information against the background of an electronic map of the city and ensure continuous tracking of moving objects, the StarView system is used, implemented on UNIX-oriented workstations or X-terminals. Stations can be combined into a network and connected to the system based on AVL Manager.
The Logiq Dispatch system is designed for dispatching long-distance freight transportation. It is implemented on the basis of satellite communication terminals of the INMARSAT system, installed on vehicles.
The original development of the PRIN company is the PRIN IDS software package, which allows for the rapid deployment of a multifunctional tracking and operational control system for a small vehicle fleet. This system will allow for continuous monitoring of vehicles, displaying the coordinates of vehicle route points on the dispatcher's electronic map, optimizing routes and traffic schedules, and promptly responding to emergency situations.
The TransnetService company” (TNS) has been present in the market of positioning systems for a long time, has significant experience in the development and implementation of systems. It offers a wide range of equipment and software, including dispatching systems for monitoring mobile objects, marine navigation systems, autonomous navigators and equipment for accumulating vehicle route parameters. The system is based on the software “Magellan-Mfor processing cartographic and navigation information of the original design, distinguished by high performance characteristics. The software is developed on a modular principle and can be easily adapted to the types of equipment used, communication systems, and change the composition of tasks in accordance with the Customer's technical specifications. It is recommended to use navigation and communication equipment from KENWOOD as on-board equipment in dispatching systems: the GPS Modem module, which includes a 6-channel navigation receiver and a radio modem, and car radio stations. The GPS Modem device is specially designed for use in dispatching systems. It implements such important functions as noise-resistant coding and compression of information, the ability to connect on-board sensors and actuators, group coding of moving objects, and synchronous mode of information transmission in a group. This allows for the efficient use of radio frequency resources and at the same time ensures a high frequency of updating information about moving objects. GPS Modem is adapted to work with radio stations f. KENWOOD, operating both in Conventional Radio mode and in trunking systems (LTR and MPT1327). However, radio stations from other companies can also be used (at the expense of some reduction in functionality).
Interesting possibilities are provided by the BNP-Trans vehicle motion parameter accumulation equipment. The equipment is installed on a mobile object (including installation hidden from service personnel) and autonomously accumulates route point coordinates obtained from GPS SRNS signals. Additionally, on-board sensor readings can be recorded (instances of opening/closing of passenger compartment or container doors, fuel flow meter, refrigerator temperature meter). The capacity of the non-volatile memory allows recording up to 20,000 waypoints, which is enough to store a vehicle route for several weeks. When processing the accumulated data, the locations of deviations from the route assignment (in time or place), attempts at unauthorized impact on the cargo, attempts at deliberate impact on the equipment (by disconnecting the on-board power supply) or the navigation antenna are determined. The accumulated information will allow route optimization, increasing the safety and cost-effectiveness of transportation. This equipment can be useful for security services of transport companies engaged in long-distance transportation, and for logistics.
Firm “Termotech” is one of the few companies that offers a virtually full range of equipment and software for positioning systems of its own design. A distinctive feature is the company's extensive experience in working with the domestic GLONASS SRNS. The basis of the system is the navigation and communication controller. It is used both as part of the onboard equipment and at control centers. The navigation and communication controller ensures control of all operating modes of radio equipment, processing of all information on board. The onboard equipment ensures round-the-clock continuous operation, continuous determination of vehicle location coordinates, automatic control of the onboard radio station operating modes, voice communication with the dispatcher, and reception of differential corrections. The navigation and communication controllers can use GPS, GLONASS and combined SRNS navigation receivers. It is possible to work with autonomous communication channels (VHF, CB), trunking systems, cellular and satellite communication channels. A terminal with a display and keyboard can be connected to the controller to display commands from the center and enter information messages by the operator. The software of the control center provides display of the location of moving objects against the background of an electronic map, calling the crew for voice communication, receiving and recording all information about events occurring in the system, signaling the operator about deviations in the specified routes of movement of vehicles, generating differential corrections.
Firm “GeoSpectrum” offers equipment that can be integrated into a wide range of radio communication systems: packet radio networks, LTR trunking systems, MPT1327, Edacs, satellite communication networks. The control center software allows for the functional inclusion of new types of communication systems. The cartographic department of GeoSpectrum” offers a wide range of electronic maps of various regions of Russia. The control center software is implemented using both the proprietary GIS “Panorama” and other GIS. The developed on-board computer module can also be used as a car navigator: when a standard car TV (Alpine, Clarion) is connected to it, an electronic map is displayed on the screen, which displays the current position of the car and provides recommendations on how to plot the optimal route. Analog or contact sensors, a small-sized video camera can be connected to the on-board computer.
KORD” Company” develops on-board equipment and data transmission facilities together with TESLA. Navigation equipment, modem and radio station are integrated into a single design block. It is possible to connect an on-board terminal with a display and keyboard. Our own data transmission protocol allows for the efficient use of the radio frequency spectrum. The control center software works with both vector and raster electronic maps.
The company “Unicom” presents the “Unicom–AVL” system based on an on-board navigation complex of our own design, connected to a standard VHF radio station. The control center software allows displaying the location of a moving object against the background of an electronic map. The number of moving objects in the system is up to 255.
The experienced reader may notice that when describing the on-board equipment, the author has not specified such a parameter as the overall dimensions of the equipment. This is done deliberately, since the dimensions of the on-board complex as a whole depend on the dimensions of the communications equipment used. The device itself, which includes a navigation receiver, controller and modem, depending on the additional functions performed (work with a display, keyboard, other external devices) can have overall dimensions from 0.5 cubic dm to 2-5 cubic dm. The dimensions of a standard automobile VHF radio station are at least 1 cubic dm.
Let's consider a number of projects presented by companies that are operators of public communication systems. For these companies, systems for operational control of mobile objects are an additional service that expands the capabilities of communication networks.
Firm “Morsvyazsputnikrepresents the interests of the Inmarsat satellite communications system in Russia. The proposed system is based on Inmarsat Standard-S satellite communications terminals with a built-in GPS receiver. The control center software provides tracking of 256 objects located anywhere on the globe from 80 degrees north latitude to 80 degrees south latitude. The polling period for objects being tracked is 15 minutes or more. The time it takes to receive information at the control center (for example, an alarm signal) is 3–5 minutes from the moment of transmission. This software can also be used in a system using conventional VHF radio channels.
Central Telegraphimplemented in Moscow the public radio packet data transmission network RADIOTEL based on technologies of Racal and Sprint. The RADIOTEL network facilities provide ample opportunities for creating distributed systems for fast and reliable data exchange in fixed and mobile environments. The vehicle dispatching system (VDS) ensures prompt tracking of the route of a vehicle equipped with a network terminal with a GPS receiver. The radio network enables data exchange between on-board equipment and the central computer, access to central databases, and interaction with emergency services and security services. The RADIOTEL network ensures fast connection establishment (approximately 5 seconds), has built-in data protection and error correction mechanisms. The network packet switching center provides support for the X.25, X.75, X.3/X.28/X.29, SNA/SDLC protocols.
Grant-Vympel Group of Companiestogether with the federal network «SOTEL» offers the GrantGuard car navigation and monitoring system based on NMT-450 standard cell phones of the Moscow Cellular Communications. The on-board navigation system is supplied in several configuration options. The minimum configuration uses a specialized navigation computer with a modem connected to a cell phone. The on-board system ensures the transfer of data on the location of the car and its condition to the control center (depending on the composition of the connected sensors), the transfer of messages on emergency situations (by pressing the panic button). The switching time of the channel with the computer of the control center can reach several minutes, but the data transfer time itself does not exceed 20 seconds, due to which the call is not charged in the telephone network. At the same time, it is possible to use the phone for voice conversations. In the extended configuration, a portable computer is connected to the navigation computer. The computer can operate in the «mobile office» mode, perform the functions of a car navigator, provide access to the information bases of the center.
Company “Mobile Telesystems(MTS) is the largest GSM cellular operator in Russia. This standard provides for wide data transmission capabilities — both via regular traffic channels and in short message mode (SMS Service). The small dimensions of GSM subscriber equipment and its high degree of integration with modern digital systems make it possible to implement an on-board navigation complex with high performance characteristics. The company offers on-board equipment manufactured by foreign companies (the DUO system by GPP, equipment by Falcon), as well as an on-board controller of its own design. Both a traffic channel (with the built-in modem also operating as a regular telephone modem at a speed of 9600) and a short message channel are used to transmit data. The switching time of the traffic channel for data transmission is 30-90 sec., the transmission time of a short message (up to 160 bytes) from one network subscriber to another (including from mobile to mobile) is 5-10 sec.
The use of cellular communication systems is justified in cases where it is necessary to reduce the dimensions of on-board equipment, the level of its own electromagnetic radiation (and, accordingly, the power consumed by the equipment from the on-board network or an autonomous power source), and also when it is necessary to ensure a large area of the system's operation. From this point of view, cellular systems cover the area of operation of short-range systems (urban, regional) and global systems (due to national and international roaming). At the same time, due to their small size and large area of operation, equipment based on cellular systems can be successfully used in comprehensive security systems for VIP-class vehicles as an alternative to systems operating on zonal principles (radio beacon systems such as Lo Jack and KORZ).
In conclusion, a few words about the cost of systems. It should be noted that only a system with limited capabilities can be relatively cheap: for operational tracking of a limited fleet of vehicles (up to 30) in a limited area (defined by the coverage area of the control center radio station). For such a system, we can say that its cost is a simple sum of the cost of the subscriber and center equipment or linearly depends on the cost of its components. For more complex systems, the dependence of the cost of the system on the cost of its components during the full cycle of its operation is nonlinear. Cheaper on-board equipment and communication system equipment may subsequently result in the need to invest large funds in obtaining or renting radio frequency spectrum resources, creating your own communication infrastructure (a network of base stations, repeaters, communication channels between base stations). In some cases, it may be advantageous to pay the tariffs of trunking or cellular public systems, despite their apparent high cost. Marketing research by some foreign companies regarding the cost of equipment and payment for services of system users (for example, owners of expensive cars or freight carriers) show that the total expenses of system subscribers should not exceed 4-5% of the value of their property. Russian manufacturers of location systems estimate the cost of on-board equipment for dispatch systems and vehicle security systems in the range from 1,000 to 2,000 dollars. At the same time, the cost of software for a dispatch center with an electronic map can vary from 2,000 to 50,000 dollars (depending on the functions performed, the number of objects of control, and the communication system used). The cost of paying for the lease of communication channels or paying for public communication networks is from $50 to 200 per month for one vehicle.