【Abstract】 Global Positioning System (Global Positioning System, referred to as GPS) through the combination of satellite signals and ground equipment, can accurately determine the location and time of any location. This paper will be divided into four parts, first introduces the development history and typical events of GPS technology, secondly explains the working principle of GPS in detail, then discusses the wide application of GPS in various industries and fields, and finally looks forward to the future development trend of GPS.
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1.GPSOverview
Global Positioning System (English:Global Positioning System, often abbreviatedGPS), also known as the global satellite positioning system, is a medium earth orbit satellite navigation system developed by the US Department of Defense and operated and maintained by the US Space Force. It can be used for most of the earth's surface (98%) Provide accurate positioning, speed measurement and high-precision standard time. The global positioning system meets the needs of military users located anywhere on the global ground or in near-Earth space to continuously and accurately determine three-dimensional position, three-dimensional motion and time.
diagram 1Global Positioning System
the system includes space31pieceGPSartificial satellite; on the ground1main control station,3data injection stations and5monitoring stations, and as a user-sideGPSmilitary receiving machines, smart phones, etc. At least only4satellites, the location and altitude of the user on the earth can be quickly determined; the more satellite signals can be received, the more accurate the decoded location will be. At the same time, because the time difference is used for positioning, the time stamp can also be accurately corrected.GPSsystem has the following advantages: the use of low-frequency signals, even if the weather can still maintain a considerable signal penetration;98%global coverage; high-precision three-dimensional fixed-speed timing; fast, time-saving, high-efficiency; wide application, multi-function; movable positioning.
The system was established by the United States Government in1970s,1978year2month, and on1994. Users only need to haveGPSreceive the chip to use the service.GPSsignals are divided into standard positioning services for civilian use (SPS,Standard Positioning Service) and military precision positioning services (PPS,Precise Positioning Service) two categories. DueGPScan be used arbitrarily without any authorization. Originally, the United States was worried that hostile countries or hostile organizations would take advantage of it.GPSan attack on the United States, the selective error was deliberately added to the civilian signal (I. e.SApolicy,Selective Availability) to reduce the accuracy so that its final positioning accuracy is approximately100meters; The accuracy of military regulations is (0.3~6meters) below.2000years later, Bill·the Clinton administration decided to remove the jamming of civilian signals. Therefore, now civilianGPScan also reach (0.3~6meters) or so positioning accuracy.
GPSsystem are as follows:
1) All-weather, not easily affected by any weather;
2) Global coverage up98%;
3) Three-dimensional fixed-point fixed-speed timing with high precision;
4) No communication between stations is required;
5) Fast, time-saving and high efficiency;
6) Wide application and multi-function;
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2.GPSTechnology Development
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2.1 predecessor
diagram 2meridian satellite positioning system
GPSsystem was the meridian satellite positioning system developed by the us military,1958,1964. The system is used56satellites works, bypassing the earth at most every day.13times, but can not give height information, in terms of positioning accuracy is not satisfactory. However, the meridian system enables the research and development department to obtain the initial experience of satellite positioning, and verifies the feasibility of positioning by satellite system,GPSlay the foundation for the development of the system. Due to the great superiority of satellite positioning in navigation and the huge defects of the meridian system in the navigation of submarines and ships, the U.S. Navy, Army, Air Force and civilian departments feel the urgent need for a new satellite navigation system.
the U.S. Naval Research Laboratory has proposed a project calledTinmation,1218satellites,10000km altitude of the global positioning network program, and in.1967year,1969year and1974, an experimental satellite was launched, and the atomic clock timing system was initially tested on these satellites.GPSsystem.
the United States Air Force proposed621-B: in each constellation45satellites34constellation, except for these satellites.1are in synchronous orbit and the rest are in use with a period24hinclined track. The plan is based on a pseudo-random code (PRN) for the transmission of satellite ranging signals based on its powerful function, when the signal density is lower than the ambient noise1% can also be detected. The successful use of pseudo-random codes isGPSsystem. The Navy's program is primarily used to provide low-dynamic2-dimensional positioning, the Air Force's program can provide highly dynamic services, but the system is too complex. Since the development of two systems at the same time will incur huge costs, and both projects here are designed to provide global positioning, so.1973, the U.S. Department of Defense will2are combined into one, and the Joint Planning Agency for Satellite Navigation and Positioning under the Ministry of National Defense (JPO) leadership, will also set up offices in the Air Force Space Office in Los Angeles. The agency has a large membership, including representatives of the United States Army, Navy, Marine Corps, Department of Transportation, Defense Mapping Agency, NATO and Australia.
2.2Plan
the initialGPSplan was born under the leadership of the Joint Planning Bureau, which will24satellites are placed on each other.120degrees on six tracks. Each track has4satellites can be observed from any point on Earth.69a satellite. In this way, the coarse code accuracy can reach100m, fine code accuracy is10m. Due to budgetary constraints,GPSplan to reduce the number of satellite launches and replace them18satellites are distributed in each other.60degrees6on a track. However, this solution does not ensure satellite reliability.1988, the last revision was made: in the process of mutual success30degrees6track has21operational satellites and3a backup satellite. This is also nowGPSthe way the satellite works.
2.3implementation
GPSplan is divided into three stages:
is the stage of scheme demonstration and preliminary design.
from1978years1979, it was launched on a Gemini rocket from Vandenberg Air Force Base in California.4test satellites, the long half axis of the satellite orbit is26560km, inclination64degrees. Track height20000km. At this stage, the ground receiver and the ground tracking network were mainly developed, and the results were satisfactory.
is a comprehensive development and testing phase.
from1979years1984, they launched again.7is calledBLOCKI's test satellite has developed receivers for various purposes. Experiments show that,GPSpositioning accuracy far exceeds the design standard, the use of coarse code positioning, its accuracy can be up14meters.
is the practical networking stage.
1989year2month14day.GPSworking satellite was successfully launched, and this phase of the satellite is calledBLOCK IIandBLOCK IIA. This phase declaresGPSsystem enters the state of engineering construction.1993, now.GPSnetwork, I .e.“21 3”GPSconstellation has been built, and the failed satellites will be replaced in the future according to the plan.
2011year6month, the U.S. Air Force successfully expandedGPSsatellite constellation, tuning6the position of the satellite and join the multi3satellites. This increases the number of working satellites27, expanded.GPSthe coverage of the system and improve the accuracy.
3.GPSsystem composition
GPSsystem is mainly composed of space constellation part, ground monitoring part and user equipment part.
diagram 3GPSsystem composition
3.1space constellation part
GPSsatellite constellation was originally designed24satellites, of which21is a working satellite,3is a spare satellite.24satellites are evenly distributed6orbital planes, I .e., each orbital plane has4satellites. The orbital inclination of the satellite's orbital plane relative to the Earth's equatorial plane is55 °, the difference between the ascension points of each orbital plane.60 °, a satellite in one orbital plane is ahead of the corresponding satellite in the adjacent orbital plane to the west.30 °. The purpose of this layout is to ensure that it can be observed at least at any place and at any time in the world.4satellites.
diagram 4GPSsatellite type
GPSsatellite was developed by the Space Department of Rockfield International, a single satellite.774kg, the service life is7year. The satellite adopts a honeycomb structure, the main body is cylindrical, and the diameter is1.5m. On both sides of the satellite are equipped with two double-leaf solar panels (BLOCK I), full length5.33m, the sunlight-receiving area is7.2㎡. The orientation system to the sun controls the rotation of the two-wing battery panels, so that the panels are always aligned with the sun, providing continuous power to the satellite and providing power to the three groups.15Ahnickel-cadmium battery charging to ensure that the satellite in the shadow of the earth can still work normally. at the bottom of the star.12units, which can transmit at an angle of about30 °Lband (19cmand24cmwave) signal. Omni-directional telemetry and remote control antennas are installed on both ends of the star for communication with the ground monitoring network. In addition, the satellite is equipped with an attitude control system and an orbit control system in order to maintain the satellite at an appropriate height and angle and accurately align it with the visible ground of the satellite.
GPSsystem shows that the higher the accuracy of the satellite clock, the higher the positioning accuracy. The early experimental satellite used a quartz oscillator developed by Hopkins University with a relative frequency stability10-11/seconds. The error is14m.1974years later,GPSsatellite uses a rubidium atomic clock with a relative frequency stability10-12/seconds, error8m.1977years,BLOCK IIuses a cesium atomic clock developed by Mas Frequency and Time Systems, with a relatively stable frequency10-13/seconds, the error is reduced2.9m.1981, Hughes developed a relatively stable frequency10-14/seconds of the hydrogen atomic clock makeBLOCK IIRsatellite is reduced to only1m.
3.2Ground monitoring part
ground monitoring part is mainly composed1main control stations (Master Control Station, shortMCS),4ground antenna stations (Ground Antenna) and6monitoring stations (Monitor Station) composition.
main control station is located at Sherifall Air Force Base in Colorado, USA. It is the management center and technical center of the entire ground monitoring system. There is also an alternate master control station in Gettysburg, Maryland, which is active in the event of an emergency. The main control station is equivalent to the entireGPSsystem, it is very important, so there are two master stations as mutual backups.
ground antenna stations currently have4are located in Guagarin Atoll in the Marshall Islands in the South Pacific, Ascension Island in the British Dependent Territory in the Atlantic Ocean, Diego Garcia Island in the British Indian Ocean Territory and Colorado Springs in the United States. The role of the ground antenna station is to inject the satellite ephemeris, navigation messages and other information calculated by the main control station into the corresponding satellite.
diagram 5all over the worldGPSground control system
ground antenna stations are also monitoring stations, as well as in Hawaii and Cape Canaveral.2monitoring station, so the monitoring station currently has6. The main role of the monitoring station is to collectGPSsatellite data and local environmental data, and then send to the main control station.
3.3User Equipment Section
diagram 6GPSUser terminal
user equipment is mainlyGPSreceiver, the main function is fromGPSsatellite receives the signal and uses the information to calculate the user's three-dimensional position and time.
4.Industry Applications
Global Positioning System has a wide range of applications in various industries and fields. Here are some of the main application areas:
diagram 7GPSApplication areas
GPSis widely used in vehicle navigation systems to help drivers plan the best route and provide navigation guidance. in addition,GPSalso plays a role in traffic management, such as traffic monitoring and intelligent transportation systems.
GPScan track the location of goods and transport vehicles, providing real-time logistics management and scheduling. This helps improve transportation efficiency, reduce costs and optimize supply chain management.
used in agricultural fieldsGPSprecision agriculture, including soil sampling, precision fertilization and precision spraying. in addition,GPSis also used in the field of environmental protection, such as wildlife tracking and natural resource management.
GPSplays an important role in the field of emergency rescue. ByGPS, rescuers can quickly locate the scene of the accident or the location of the trapped people and provide timely rescue and assistance.
GPSis widely used in earth science research, for measuring crustal movement, geological structure and earthquake monitoring. In the field of space,GPSis also used to navigate and locate space probes.
5.future development trend
diagram 8GPS
GPS will continue to evolve and evolve as technology continues to advance and demand increases. Here are some possible future trends:
improve accuracy and reliability: the futureGPSsystems may further improve the accuracy and reliability of positioning to meet higher demands. New techniques and algorithms will be introduced to reduce signal interference and improve measurement accuracy.
multimodal navigation: The futureGPSsystem may be integrated with other navigation technologies, such as inertial navigation and visual navigation, to form a multi-modal navigation system. This will provide a more robust and comprehensive navigation solution.
indoor positioning: currentGPSsystems mainly provide positioning services in outdoor environments, positioning in indoor environments still faces challenges. the futureGPSsystems may develop indoor positioning technology, through the combination of other technologies (such as wireless signals and sensors), to achieve accurate positioning in large buildings, shopping malls and airports and other indoor environments.
Autonomous driving and intelligent transportation: With the development of autonomous driving technology,GPSin intelligent transportation systems will become more important. the futureGPSsystem may be integrated with the vehicle's autonomous driving system to provide high-precision location information and navigation guidance to promote the development of intelligent transportation.
to expand into a broader field: in addition to existing application areas, futureGPSsystems may also be extended to broader areas. For example, in virtual reality and augmented reality,GPScan be used for location tracking and augmented reality experiences. in addition,GPScan also play a role in emerging IoT applications, such as smart cities, smart homes, and smart health.
Generally speaking, GPS will continue to develop and evolve under the impetus of continuous technological innovation and application needs. the futureGPSsystem will be more accurate, reliable, and expand to more areas, bringing more convenience and innovation to human life and various industries. whether in navigation, logistics, scientific research or other fields,GPSwill continue to play an important role and become one of the key technologies to promote social progress.
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