radio navigation systems

*RADIO NAVIGATION SYSTEMSINTRODUCTION

RADIO NAVIGATION SYSTEMS

* Definitions of NavigationINTRODUCTION 1.1 DEFINITIONS Navigation is the determination of the position and velocity of a moving vehicle.


* Guidance Guidance is Any of various processes for guiding the path of a vehicle, especially a missile, by means of built-in equipment. (1) Steering toward a destination of known position from the aircrafts present position.

(2) steering toward a destination without explicitly measuring the state vector.Some related conceptions 1.1 DEFINITIONS


* Navigation system is the general designation of the equipment or equipment combination which afford the navigation service for vehicle. The navigation system emphasizes on the equipment combination which can achieve some navigation function. In general, Navigation equipment is one type of set which can achieve single function in the navigation system.Some related conceptions Navigation System & Navigation Equipments1.1 DEFINITIONS


*INTRODUCTIONpositioning systemsEach one has frame of reference. Radio systems Celestial systems. Mapping navigation systems.(emphasis)1.2 CATEGORIES OF NAVIGATION(1)According to whether or not continuous positioning data are dependant


*INTRODUCTION1.2 CATEGORIES OF NAVIGATIONDead-reckoning navigation systems Measuring aircraft heading and either speed or acceleration. Measuring emissions from continuous-wave radio stations. Recording and integrating the variation of position continuously.


*Celestial navigationInertial navigation Radio navigationGeomagnetism navigation Infrared Navigation

(3)According to the technical means 1.2 CATEGORIES OF NAVIGATION


*Laser NavigationSonar Navigation Mapping navigation Way points or lighted beacons navigation1.2 CATEGORIES OF NAVIGATION(3)According to the technical means


*1.3 The category of radio navigation system (1) According to the relation between onboard equipments and navigation stations. Active radio navigation system. Negative radio navigation system


*(3) According to the maximum coverage of navigation system Short-range radio navigation system: range of action is about 500 kmMid-range radio navigation system: range of action is about 1,000 kmLong-range radio navigation system: range of action is about 3,000kmSuper-long-range radio navigation system: range of action is over 10,000km, some of them can cover the whole global. 1.3 The category of radio navigation system


* We can use state vector to describe the translational motion of the vehicle. In the air the state vector have six-component: three components of position and the three components of velocity.1.4 Navigation Nomenclature and Glossary


*(x,y,z)The state vector:


*TIMELocal timeUniversal Time (Greenwich Mean Time, GMT)Atomic Time (AT)Universal Coordinate time (UTC)System time


* HDGHeading: The tail to nose direction of the aircraft longitudinal axis measured in degrees clockwise form either magnetic or true North. POS: Position WPT Waypoint: a significant point on the route which may be used for reporting to Air Traffic Control, turning of landing.


*HDGHeading:Ture NorthMagnetic NorthThe tail to nose directionNavigation station


*INTRODUCTION 1. Cost. 1.6 DESIGN TRADE-OFFS The selection of navigation system consider the following attributes: 2. Accuracy of position and velocity.3. Autonomy.4. Time delay in calculating position and velocity, caused by computational and sensor delays. 5. Geographic coverage.


*INTRODUCTION7. Availability. 1.6 DESIGN TRADE-OFFS8. System capacity. 9. Ambiguity. 10. Integrity. 6. Automation. The selection of navigation system consider the following attributes:


*INTRODUCTION1.7 EVOLUTION OF AIR NAVIGATION1. Visual navigation An anemometer for airspeed; A barometer for altitude; A magnetic compass for heading; Artificial horizons and turn-and-bank indicators allowed pilots to hold attitude and heading in clouds.


*INTRODUCTION2. Lighted beacons 1.7 EVOLUTION OF AIR NAVIGATION Lighted beacons were installed across the United States in the 1920s to mark airmail routes.


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*INTRODUCTION6. Downward-looking telescope. 1.7 EVOLUTION OF AIR NAVIGATION From the 1930s to the 1960s, drift angle (DA) was measured in flight with a downward-looking telescope that observed the direction of movement of the ground, when it was visible.


*INTRODUCTION From the 1940s to the 1960s, drift was estimated over oceans by observing trends in the difference, D, between the readings of the radio altimeter and pressure altimeter. 7. Observing trends in the difference. 1.7 EVOLUTION OF AIR NAVIGATION


*INTRODUCTION8. Doppler and inertial navigators1.7 EVOLUTION OF AIR NAVIGATION In 1960s and 1970s, the introduction of Doppler and inertial navigators allowed drift to be observed directly.They are independent navigation system. The Doppler navigator measures the direction of the ground-speed vector relative to the aircraft's centerline. The inertial navigator subtracts in-measured airspeed from the measured ground velocity to calculate wind, hence lateral drift.


*INTRODUCTION9. VOR , ILS and VOR/DME (radio navigation)1.7 EVOLUTION OF AIR NAVIGATION After World War II, VOR (Very-high-frequency Omnidirectional Range) stations (Chapter 3) and Instrument Landing Systems (ILS, Chapter 4) were installed. VOR/DME and ILS have been the basis of navigation in western countries ever since. Now, they are adopted for use by the International Civil Aviation Organization(ICAO).


*INTRODUCTION10. Surveillance radar (radio)1.7 EVOLUTION OF AIR NAVIGATION During the 1960s, air-traffic controllers came to rely on surveillance radar in densely populated airspace (Chapter 5). The controller identified the aircraft on his screen, hence eliminating the need for a position report from the crew.


*INTRODUCTION Radar surveillance of air traffic is called positive control, which, in 1996, existed in the United States, most of Canada, Western Europe, and Japan. 1.7 EVOLUTION OF AIR NAVIGATION10. Surveillance radar In the late 1990s, the automatic reporting of on-board-derived position began to supplement (perhaps eventually to replace) radar surveillance.


*INTRODUCTION11. RSBN1.7 EVOLUTION OF AIR NAVIGATION Since the late 1960s, The former Soviet republics domestic civil and military aircraft have used an L-band range-angle system known by its Russian acronym, RSBN, and not standardized by ICAO.


*INTRODUCTION 12. Precision approach radar (PAR) 1.7 EVOLUTION OF AIR NAVIGATION In 1942 PAR came to use, now just as in commercial aviation, PARs are seldom used because they depend on a trained operator. PARs operators keep a close watch on the screen to know positions of the landing airplane, tell the information to the pilot by radio, command the pilot for landing.


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*INTRODUCTION13. hyperbolic radio-navigation system1.7 EVOLUTION OF AIR NAVIGATION Hyperbolic radio-navigation systems are long range navigator. They are Loran-A, Loran-B, Loran-C, Loran-D, Omega, Chayka, Decca and so on.


*INTRODUCTION13. hyperbolic radio-navigation system1.7 EVOLUTION OF AIR NAVIGATION Just before the outbreak of World War II in Europe, the Loran-C begun into use. Now it provides a valuable service in many parts of the world,in particular the north and east Pacific and Atlantic. The system is used by many ships and aircraft and world appear to have an indefinite future. It uses ground waves at low frequencies, thereby securing an operating range of over 1000 mi.


*INTRODUCTION Omega, Omega signals are sub-ionospheric; that is, they are propagated between the earth surface and the D-region of the ionosphere. Because VLF signal attenuation is low, the signals are propagated to great ranges, typically 5000 to 15,000 NM. 1.7 EVOLUTION OF AIR NAVIGATION13. hyperbolic radio-navigation system


*INTRODUCTION Decca, Decca system developed by the British and used extensively during the later stages of World War II. In 1996, its major area of implementation is in northwestern Europe where it is primarily used by shipping companies. 1.7 EVOLUTION OF AIR NAVIGATION 13. hyperbolic radio-navigation system


*INTRODUCTION Chayka systems Chayka (meaning sea gull) is a pulse-phase radio-navigation system similar to the Loran-C system. It is used in Russia and surrounding territories and seas. By using ground waves at low frequencies, the operating range is over 1000 mi. 1.7 EVOLUTION OF AIR NAVIGATION 13. hyperbolic radio-navigation system


*INTRODUCTION During the late 1960s, the requirements of civil aviation were forecast to exceed the capabilities of the ILS. The U.S. military services, for more than a decade, had been developing microwave approach guidance systems to support tactical deployments and aircraft-carrier operations. This is called Microwave Landing System MLS.1.7 EVOLUTION OF AIR NAVIGATION14. MLS


*INTRODUCTION15. GPS and GLONASS1.7 EVOLUTION OF AIR NAVIGATION GPS and GLONASS are based on one-way passive range measurements to several stations, most of which are spacecraft The receiver in the airplane uses the signal of GPS/GLONASS to compute position, velocity, the offset in the airborne clock, and, in some receivers, the ionospheric delay.


Figure 1.2

radio navigation systems

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