Ensuring GPS navigation integrity using receiver autonomousintegrity monitoring

The many advantages of Global Positioning System (GPS) based navigation have created a tremendous amount of interest in using GPS as the primary navigation aid onboard commercial and civil aircraft. Even in the presence of Selective Availability, the accuracy of GPS is sufficient to guide aircraft point-to-point between airports without requiring other navigation aids such as VOR or DME. Unfortunately, there is a finite probability that a GPS satellite will fail, causing the transmission of potentially misleading navigation information. Thus, before GPS can be widely adopted as a navigation aid, techniques must be devised to detect any possible failures and notify the user prior to the degradation of navigation accuracy. This paper discusses the problem of detecting possible GPS satellite failures using a technique called Receiver Autonomous Integrity Monitoring (RAIM)     

Preliminary Evaluation of GPS Performance for Low-Cost General Aviation

Preliminary results of a simulation effort to evaluate the requirements and feasibility of the global positioning system (GPS) as a civil air navigation system are presented. Evaluation is made of GPS requirements, from operational considerations, such as application to nonprecision approaches. The conceptual low-cost GPS receiver simulated here does not correct for the ionospheric or trophospheric delay, is sequential in nature, tracks only four satellites, and is not mechanized to make independent range rate measurements based on the Doppler shift of the GPS carrier frequency. The proposed GPS system has significantly different performance characteristics from the presently used VHF omnidirectional range (VOR) solidus distance-measuring equipment (DME) system. The GPS is a low signal level system and many have a relatively slow data rate due to the low-cost sequential receiver design. The results indicate that although the conceptual low-cost GPS receiver/ navigator is potentially more accurate than a VOR, the accuracy may degrade during aircraft turns and satellite shielding periods.     

基于交互式多模型的飞机编队相对导航算法研究

在飞机编队飞行时,成员间的相对位置信息是实现系统协同作战的重要保证,为了提高机群编队飞行的相对导航定位精度,在无地面基准的机群编队飞行JTIDS/GPS/TACAN/IFDL组合的相对导航系统中,采用交互式多模型扩展卡尔曼滤波(IMM-EKF)算法,设计实现了多传感器相对导航系统,克服了飞机动态模型参数变化导致使用单一动态模型滤波精度下降的问题。仿真分析结果表明,交互式多模型算法可以提高相对导航系统的定位精度和可靠性,特别在GPS可见卫星很少的情况下,依然能够具有良好的定位性能。     

Navigation system of pilotless aircraft via GPS

The pilotless aircraft has wide applications in measuring earth, surveying mineral sources, fireproofing in the forest, observing floods and so on. In this paper, after briefly introducing positioning and navigation technologies for pilotless aircraft-a new kind of navigation system for pilotless aircraft using GPS (Global Positioning System) is presented. An overall plan of the navigation system is discussed, and its technology cruxes are analysed. Its hardware and software are designed and implemented, and experimental results are given. The navigation system not only has autonomous navigation capability, but can also achieve navigation aided by telecontrol system. It can supervise flying by telemetering system and displaying predetermined air line and flight path maps on the computer monitor. It can run in simple GPS receiver mode or in the differential GPS mode by means of available telecontrol channel. These are, no doubt, of great value for the navigation of pilotless aircraft     

Decentralized Filtering and Redundancy Management for Multisensor Navigation

Failure detection and redundancy management is discussed for avionics applications of integrated navigation involving coordinated use of multiple simultaneous sensor subsystems such as GPS, JTIDS, TACAN, VOR/DME, ILS, an inertial navigation system (INS), and possibly even Doppler AHRS. A brief high level survey is provided to assess the status of those techniques and methodologies advertized as already available for handling the challenging real-time failure detection, redundancy management, and Kalman filtering aspects of these systems with differing availabilities, differing reliabilities, differing accuracies, and differing information content/sampling rates. Following the status review, a new failure detection/redundancy management approach is developed based on voter/monitoring at both the raw data and at the filtered-data level, as well as using additional inputs from hardware built-in-testing (BIT) and from specialized tests for subsequent failure isolation in the case of ambiguous indications. The technique developed involves use of Gaussian confidence regions to reasonably account for the inherent differences in accuracy between the various sensor subsystems. Online estimates of covariances from the Kalman filter are to be used for this purpose (when available). A technique is provided for quantitatively evaluating both the probability of detecting failed component subsystems and the probability of false alarm to be incurred, which is then to be traded off as the basis for rational selection of the thresholds used in the automated decision process. Moreover, the redundancy management procedure is demonstrated to be amenable to pilot or navigation operator prompting and override, if necessary.     

Receiver autonomous integrity monitoring (RAIM) capability forsole-means GPS navigation in the oceanic phase of flight

Receiver autonomous integrity monitoring (RAIM), a GPS integrity monitoring scheme that uses redundant ranging signals to detect a satellite malfunction that results in a large range error, involves two functions: detection of the presence of a malfunctioning satellite and identification of which satellite (or satellites) is malfunctioning. An analysis is presented of GPS RAIM capability for sole-means navigation in the oceanic phase of flight, where the position protection limit requirement for the integrity function is not as stringent as for nonprecision approaches, and yet both detection and identification function may be required if GPS is to be used as a sole-means system. For this purpose, a detection and identification algorithm is developed which takes advantage of the fact that for the oceanic phase of flight, a much larger position error is acceptable than for the nonprecision approach phase of flight. The performance of this algorithm and an algorithm proposed previously by others is estimated via simulation and compared. On the basis of the results, recommendations are made on how RAIM may be used if GPS is to be coupled with an inertial system to provide a sole-means capability in the oceanic phase of flight     

卫星导航系统发展动态

卫星导航系统是20世纪60年代中期发展起来的一种新型导航系统，90年代，卫星导航时入全运行和盛行时期，除了用于陆上，海上和空中的航行引导外，几乎扩展到军事和经济的各个方面，目前，除了已经运行的美国的GPS（全球定位系统）和俄罗斯的GLONASS（全球导航卫星系统）外，欧盟也正在积极开发伽利略系统。本文分别介绍GPS、GLONASS和伽利略系统的发展状况。     

GPS Program Status

The Navstar Global Positioning System (GPS) Program is composed of three segments ? Space, Control, and User Equipment. The Space segment is responsible for the development and launch of the GPS satellite constellation. The Control segment is responsible for monitoring the satellite telemetry and providing updated navigation information to the satellites. The User Equipment (UE) segment is responsible for the development and procurement of the GPS receivers for a variety of host vehicle platforms. Recently, approval was given to the User segment to enter Low Rate Initial Production (LRIP). This approval marks the beginning of Phase III (production and deployment) of the GPS program. This paper will discuss the overall status of all three segments with an emphasis on the User Equipment segment as it enters the production phase of the program.     

Global Positioning System-the newest utility

The Global Positioning System (GPS) has become the high tech utility of the 20th century. It was developed by the US Department of Defense as a precise navigation reference for the military services. Although the signal available to civilian users had been purposely degraded in what is called selective availability (SA), it is one of a few technological success stories that had positive unintended consequences. Recent announcements indicate that this SA impediment has been removed. GPS currently has a huge civilian market in commercial and private aviation, ship navigation, mapping and surveying, telecommunications position determination, and recreational boating and hiking. By 2003 sales of GPS based products are expected to be $16 billion     

GPS/INS integration on the Standoff Land Attack Missile (SLAM)

The Standoff Land Attack Missile (SLAM) is a worldwide, all-weather, precision-strike weapon system deployed from carrier-based aircraft. In the primary mode of operation, target location and other mission data are generated from intelligence sources available on the aircraft carrier and loaded into the missile prior to aircraft takeoff. After missile launch, the SLAM inertial navigation system (INS) guides the missile along the planned trajectory. Updating the missile INS from the Global Positioning System (GPS) during flight provides precise midcourse navigation and enhances target acquisition by accurate, on-target pointing of the SLAM Maverick seeker. The GPS/INS avionics and software integration used for SLAM are described in detail, along with some of the design tradeoffs that led to the approach. The avionics configuration integrates the Harpoon midcourse guidance unit, which includes a strapdown inertial sensor package and digital processor, with a Rockwell-Collins single-channel, sequential GPS receiver processor unit (RPU), a derivative of the GPS phase-III user equipment. In addition to the GPS receiver elements the RPU contains the navigation processor, which executes the SLAM navigation, Kalman filter algorithms, and other guidance algorithms including seeker pointing. Flight-test results of the SLAM GPS-aided INS are also included     

塔康仿真系统的设计

塔康是战术空中导航系统,能完成测距和测位的任务。塔康仿真器是具有塔康设备功能的计算机仿真系统,它可以代替塔康设备参与航空电子系统的综合试验,而且能取得很好的效果。本文在分析塔康工作原理的基础上,对塔康仿真器的硬件结构和软件设计做了较为详细的介绍,同时,对塔康信标的仿真也做了扼要的说明。     

Measuring Aircraft Carrier Flexure in Support of Autonomous Aircraft Landings

This paper quantifies the experimental measurements of aircraft carrier flexure (deformation) at sea in support of the United States Department of Defense sea-based Joint Precision Approach and Landing System (JPALS) that aims to deliver automatic landing capabilities to inbound aircraft aboard aircraft carriers. The methodology for measuring ship flexure using the Global Positioning System (GPS) and inertial sensors is described. Results indicate that flexure on the aircraft carrier used for testing has a standard deviation of approximately 1–2 cm. For the ship tested, the most significant flexure effects are in the port/starboard direction and correlate best with roll or lateral acceleration.     

Preoperational testing of data link-based air traffic managementsystems in Magadan, far East Russia

The Global Positioning System (GPS) has been used in many ways which were unimagined by its original planners and implementers. This paper discusses one such application; the surveillance of commercial aircraft in a developing airspace environment. GPS provides system users with the ability to determine their own position with an accuracy, reliability and cost that is unprecedented. Voice procedures augmented by radar have been the primary tools for air traffic surveillance since the end of World War II. But for some countries the equipage of aircraft with GPS and a data link capable of carrying position reports to the ATC authorities is providing a viable alternative to long-range secondary radar systems. In the summer and fail of 1995, ARINC installed and demonstrated equipment in Magadan, Russia which permits air traffic controllers of MagadanAeroControl to monitor GPS position reports generated by aircraft as far away as Canada and the South Pacific. The position reports were displayed against maps and flight tracks. This equipment has clearly demonstrated an alternative technology for the upgrading of the ATC system in Siberia and other remote areas     

Navigation sensors and systems in GNSS degraded and denied environments

Position, velocity, and timing(PVT) signals from the Global Positioning System(GPS)are used throughout the world but the availability and reliability of these signals in all environments has become a subject of concern for both civilian and military applications. This presentation summarizes recent advances in navigation sensor technology, including GPS, inertial, and other navigation aids that address these concerns. Also addressed are developments in sensor integration technology with several examples described, including the Bluefin-21 system mechanization.     

Aviation electronics/avionics

International regulations prohibit aircraft from entering high-density airspace and heavily trafficked over-ocean airways without suitable avionics. The widespread use of GPS navigation and increasing complexity of passenger entertainment systems have become the latest electronics trends on large commercial aircraft. The cost of avionics plus software is approaching 50% of the total. New aircraft have multiple computers and millions of lines of software. The following sections present the most important avionics subsystems and highlight some differences between military and commercial aircraft     

航模直升机微型组合导航与控制系统研究

以JR-260型航模直升机为研究对象,基于嵌入式Linux操作系统,开发一套微型组合导航与控制系统。系统硬件采用了组合导航系统MNAV100CA和嵌入式飞行控制计算机Stargate,集成了固态的加速度计、角速率传感器、磁航向计、大气机和GPS接收机,以及R/C接收机脉位调制（PPM）航模舵机接口。软件设计采用扩展的卡尔曼滤波和状态监视方法实现了导航系统设计,基于实时Linux线程机制编制了航模舵机的驱动程序,以802.11b无线网络实现空中飞参信号的实时下传,并在便携式地面站上实现了实时监控功能。     

Navigation and landing [A century of powered flight 1903-2003]

Navigation and landing for the first half century of aviation fundamentally relied on radio-based electronic aids. The military began serious investigation of radio navigation during World War I. Up until WW II map reading, dead reckoning, and various means of radio direction finding were the primary methods of determining aircraft position. Since WWII a number of other navigation techniques, such as Doppler radar, radio inertial, pure inertial, aided inertial, and today's integrated GPS inertial, have been developed. Most of the inertial systems evolved from the military ICBM and subsequent space programs.     

飞机导航系统校准技术探讨

飞机导航系统是引导和保障飞机安全飞行的关键系统,其所涉及的一些主要参数（如VOR方位、TACAN方位、进近着陆距离、下滑轨迹等）是典型的专用参数,采用普通的方法很难准确地校准这些参数,同时由于缺少直接的国家（国防）最高标准,溯源也很困难。本文以区域导航系统为例,就其校准系统发展的特点、现有校准方法的优缺点、现有计量技术的瓶颈及解决设想等方面做些探讨性的研究,以期能够更好地解决现有军（民）机导航系统专用计量参数的溯源和量传中存在的问题。