Gps navigation

Application of GPS in navigation and aviation navigation

1.GPS navigation application

The application of satellite technology in maritime navigation can be traced back to the first generation satellite navigation system TRANSIT in 1960s. However, this satellite navigation system originally serves the polar regions, so it can't navigate continuously, and the positioning time interval changes with latitude. Above 70 degrees north and south latitude, the average positioning interval is no more than 30 minutes, but it takes 90 minutes near the equator. The second and third generation transit satellites NAVARS and OSCARS launched in 1980s make up for this deficiency, but it still takes 10 to 15 minutes. In addition, Doppler velocimetry technology is also difficult to improve the positioning accuracy (it needs to know the ship speed accurately), and it is mainly used for two-dimensional navigation. The appearance of GPS system overcomes the limitations of public transport system, which not only has high precision, continuous navigation and strong anti-interference ability; It can also provide seven-dimensional space-time position and speed information. In the initial test of pilot navigation equipment, GPS shows that it can replace bus and subgrade radio navigation systems and play an epoch-making role in navigation. Today, it is hard to imagine a ship without GPS navigation system and equipment. Navigation application has become the largest user of GPS navigation application, which is unmatched by users in any other field. There are many users of GPS navigation, and the classification standards are different. According to the route type, GPS navigation can be divided into five categories: ocean navigation; Coastal navigation; Port navigation; Inland navigation; Lake navigation. At different stages or regions, the requirements for navigation safety are different due to different environments, but they all aim at ensuring the minimum navigation traffic conflict, making the most effective use of increasingly crowded routes, ensuring navigation safety, improving transportation efficiency and saving energy. According to the function of navigation system, there are roughly the following categories:

1. 1 autonomous navigation

The autonomous navigation system is suitable for any of the above five routes. It is basically a simple navigation system. Its main feature is that it only provides users with information such as position, speed, course and time, and can also include chart track display without communication system. Suitable for any ship sailing on the sea, lakes and inland rivers, from large ocean-going freighters to private yachts.

1.2 port management and port guidance

The system is mainly used for ship dispatching management and ship guidance in ports/docks to ensure the safety and order of navigation in ports/docks. The system needs two-way data/voice communication, which is convenient for navigators to guide ships. Port situation/chart display to show the berthed ships and the inbound routes that can avoid collision. This kind of system requires high accuracy of navigation system, and differential GPS and other enhancement technologies should be adopted.

1.3 route traffic management system

This system is similar to 2, but it is mainly used for navigation and management of ships in offshore and inland waterways, and usually needs the support of satellite communication systems, such as INMARSAT.

1.4 tracking and monitoring system

This system is mainly used for maritime patrol boats, anti-smuggling boats and various yachts, especially private yachts, to prevent theft. According to specific users, some systems need to give navigation parameters and two-way data/voice communication, such as anti-smuggling boats. Sometimes it is not necessary to give navigation parameters, for example, for private yacht theft prevention, only one-way data communication is needed. In case of theft, the navigation system on the yacht will continuously send its position and course to the relevant center for tracking.

1.5 emergency rescue system

The system includes amphibious aircraft, helicopters and land vehicles. It is suitable for all five types of air routes, and is used to search and rescue all kinds of ships and people in distress at sea, lakes and inland rivers. This system requires two-way data/voice communication, fast response time and high positioning accuracy.

Application of 1.6 GPS/ sonar combination in underwater vehicle navigation

This combined system can be used for underwater operations such as underwater pipeline laying and maintenance (visual system is needed), hydrological survey, etc., such as underwater survey of ports/docks, so as to remove the blockage in the approach channel and ensure the smooth navigation channel, and can also be used for offshore fishing, fishing boat operation guidance and so on.

1.7 Other applications

The main navigation technologies used are: GPS (GNSS); Sonar technology; INS chart; Radio navigation technology; Image matching technology; Other technologies.

The communication technologies used mainly include: frequency modulation, one-way data/voice communication of TV subcarrier; Two-way data communication of beacon network: trunking communication; Cellular communication; Land-based mobile digital communication; Satellite mobile communication; Traffic trajectory communication, etc.

The first five communication technologies are mainly used in offshore, inland and lake areas.

2.GPS aviation navigation application

Although in the sense of pure technological innovation and progress, the first generation of Zhongtian satellite navigation system initiated a new era of navigation technology. However, Zhongtian has not been applied in the field of aviation navigation, and the real application of satellite navigation technology in aviation navigation can be said to begin with GPS system. In the early 1970s, when the GPS project was in the gestation and scheme demonstration stage, some people proposed to use a limited combination of GPS satellites and altimeters to realize aircraft navigation, approach and take-off, and conducted a lot of simulation research. In the early 1980s, that is, 1983, there were only five GPS satellites at that time. Rockwell's commercial plane SABRELINER (Sabre) carried impartial observers and several guests of Aviation Weekly and Space Technology, and made its maiden voyage from Iowa, USA to Paris, France. Its navigation system adopts single-channel dual-frequency military GPS receiver and single-channel single-frequency civil GPS receiver for full GPS navigation, with four times in the middle. This GPS navigation is successful, but FAA officials still have reservations and doubts about using GPS for aviation navigation. These doubts are mainly manifested in the following aspects: (1) the availability of choice; Continuity and availability of coverage by five satellites; Perfect question; Fees (including user system price and GPS fee); Selective availability affects the accuracy, perfection, availability and service continuity of GPS navigation system, and affects the reliability and navigation safety of GPS used in aviation navigation. The price of user's GPS navigation system and equipment and the charging standard of GPS are directly related to the user's affordability. In the late 1980s and early 1990s, the price of GPS users' equipment decreased year by year, and the volume became smaller and smaller. Various enhancement technologies, differential technologies and combination technologies are becoming more and more mature, and GLONASS is fully installed and put into use, which brings broad prospects for the application of GPS in aviation navigation. It can be predicted that GPS will make global seamless navigation and surveillance possible, which will be an epoch-making revolution in the history of aviation navigation. Nowadays, the application of GPS in aviation navigation can be said to be pervasive. If divided by route type or aircraft stage, it involves: foreign airspace routes; Inland airspace routes; Terminal area guidance; Approach/landing; Airport site monitoring and management; Navigation in special areas, such as agriculture and forestry. In different flight sections and different application occasions, the requirements for accuracy, perfection, availability and service continuity of navigation system are different, but the safety of aircraft flight and the effective use of airspace must be ensured. According to the function division of airborne navigation system, the application of GPS in aviation navigation is as follows:

2. 1 route navigation

The air route mainly refers to the air route in the ocean area and continental airspace. Various studies and experiments have proved that GPS and a technology called receiver autonomous integrity monitoring (RAIM) can meet the requirements of GPS for navigation accuracy, completeness and availability of ocean routes, and the accuracy can also meet the requirements of mainland airspace routes. GPS and wide-area augmentation system can also meet the requirements of accuracy, integrity and availability of continental airspace routes. The accuracy of GPS is far superior to any existing airline navigation system. This improvement of accuracy and continuous service will help to effectively use airspace, achieve the best airspace division and management, air traffic flow management and flight path management, open up broad application prospects for air transport services, reduce operating costs and ensure the flexibility of air traffic control. GPS is global, all-weather and error-free, and it is the best navigation system on medium and long-distance routes at present. According to the deployment of ICAO, GPS will gradually replace other existing radio navigation systems. GPS does not depend on ground equipment, and can be used for route planning and route penetration together with airborne computers and other equipment, which adds a lot of flexibility to the navigation of military aircraft.

2.2 Approach/Landing

Including non-precision approach/landing, CAT- 1, 2 and 3 precision approach/landing. GPS and its wide-area augmentation system fully meet the requirements of clarity, integrity and availability for non-precision approach/landing. The local pseudo-range difference technology/system enhancement can meet the requirements of CAT- 1 and 2 precision approaches. At present, experiments show that the accuracy can meet the requirements of CAI-3b level by using carrier phase difference technology. To be sure, various enhanced combined systems (such as LAAS, WAAS, INS, etc. ) and GPS will become the main means of approach/landing, and instrument landing will eventually be replaced. Because the equipment of GPS landing system is simple and does not need complicated ground support system, it will be suitable for any airport, including private airports and mountainous airports. Theoretically, the GPS landing system can guide the plane to land along any flight profile and approach route, which enhances the flexibility and blind landing ability of various airports.

2.3 On-site monitoring and management

Include terminal flight management and airport scene monitoring/management. The purpose of scene monitoring management is to reduce the detention time of take-off and approach, monitor and dispatch aircraft, vehicles and personnel at the airport, make the most efficient use of terminal space and airport, and ensure flight safety. GPS, digital map and digital communication link provide brand-new technology for developing advanced on-site navigation, communication and monitoring system. It is believed that on-site monitoring and management based on GPS/ digital map will bring great benefits to the airport.

2.4 route monitoring

At present, surveillance is an irrelevant surveillance system, which mainly uses various radar systems and can be used as a backup with the airborne navigation system. However, the ground and airborne equipment of this monitoring system is complex and expensive, and the monitoring accuracy varies with distance, and the range is limited, so it is impossible to achieve global coverage and global seamless monitoring. The appearance of GPS and aviation mobile satellite system will change this traditional monitoring mode. Airborne GPS navigation system automatically reports its position through communication. This kind of "automatic associated monitoring system advertisement" has been proposed. The current demonstrations and experiments prove that ADS will bring benefits to the monitoring of all stages of flight, especially to realize the automatic monitoring service of airspace in marine areas and remote inland areas. This will effectively reduce the workload of pilots/controllers and increase the flexibility of air traffic control.

2.5 Flight tests and tests

In the design, finalization and test of new aircraft, new airborne equipment, airborne weapon system or ground service system, the flight state parameter measurement system based on GPS may be used as a benchmark, and comparable auxiliary equipment will make flight test, data processing and flight test simple and cost-saving.

2.6 Application of Special Aircraft

Aircraft take-off and landing guidance system on aircraft carrier, helicopter temporary take-off and landing guidance, military aircraft formation, penetration, aerial refueling, aerial search and rescue, etc.

2.7 aerial survey

In addition to the navigation, take-off and landing functions required by ordinary aircraft, aircraft used for aerial survey also need to provide timely information cross-linking, data recording and post-processing to record the position of measuring or photographing equipment.

2.8 Other applications

Such as flight training, checking ILS system, etc. Although ITS is often used as a benchmark system to evaluate the capability of DGPS landing system in the current DGPS approach/landing demonstration flight, the accuracy of DGPS is actually better than that of ILS system. Before ILS is closed, DGPS is used for inspection, which is a cheap and completely accurate benchmark system for checking ILS. At present, optical measurement and radar are expensive, and the equipment is huge and complicated. Of course, the above does not include all aspects of GPS application in aviation, and new application methods are still being tested and developed.