CALCM-the untold story of the weapon used to start the Gulf War

The Conventional Air Launched Cruise Missile (CALCM) was developed from the strategic ALCM, AGM-86, by integrating GPS navigation into the missile in place of terrain correlation (TERCOM). In addition, the nuclear warhead was replaced by conventional explosives. The CALCM was developed, tested, and fielded in a single year (mid-1986-mid-1987) by the Boeing Company where the author was then employed. Although the GPS technology used, a Rockwell single channel aided receiver, has been eclipsed by newer receivers with additional capabilities and newer technology, many innovative things were done in completing the CALCM integration: the external loading of almanac data along with other mission data, three satellite navigation capability, and the use of a single channel receiver in a dynamic flight environment. This effort demonstrated that GPS outputs can be integrated quickly into an existing weapon system using the traditional loosely coupled “cascaded filter” approach. Although this approach is not as ideal as a tightly coupled integration using raw GPS data, the use of cascaded filters resulted in a weapon that was able to be rapidly fielded. The Air Force had sufficient confidence in the missile, that after four years of operational testing, 35 of these missiles were targeted at key sites at the start of the Gulf War in 1991. This effort, which was declassified in 1992, resulted in the first weapon in the DoD inventory to be operational using GPS navigation. The effort deserves consideration as a model as to how GPS integration can be performed     

Passive localization of moving emitters using out-of-planemultipath

The purpose of this work is to establish how a moving emitter, such as a jammer, can be localized by a passive receiver through the use of out-of-plane multipath signals reflected by the terrain. This is a novel localization technique that assumes no a priori knowledge of the localization of the multipath sources. The emitter parameters of range, heading, velocity, and altitude are estimated by exploiting the correlation between the direct-path signal and the delayed and Doppler modulated signals. Two basis assumptions about the scattering properties of the terrain lead to different maximum likelihood estimators (MLEs). The Cramer-Rao lower bounds (CRLB) are used to study estimator performance versus emitter velocity for each case. The proposed estimators are successfully demonstrated using field data collected at White Sands Missile Range (WSMR) during the DARPA/Navy Mountaintop program     

一种高效的数字地图高程数据存储格式

分析了DMA的DTED和USGS的DEM高程数据存储格式，比较了其异同，提出了一种高效的数字地图高程数据的存储格式并实现了存取算法。实验表明，该存储格式结构简单、便于扩展、容易实现，是一种Windows下进行数字地图数据交换的有效的文件存储格式，已经被用于数字地图三维可视化软件Terrain和新近开发的综合低空突防系统分布式仿真平台中作为数字地图数据的交换格式。     

GPS/BDS组合定位精度分析

随着定位技术的不断发展及多系统导航定位技术的逐步推广,多系统组合导航定位已经成为了GNSS导航定位领域中的主要发展趋势。主要阐述了GPS/BDS组合相对定位的观测方程和数学模型,并根据实测数据对比分析,从卫星可见性、精度因子、定位精度和均方根误差等方面对GPS、BDS及GPS/BDS组合定位系统的定位性能、定位精度进行了比较。研究结果表明,较单一的GPS和BDS系统定位,采用GPS/BDS组合定位可有效提高卫星可见数目和DOP值,且稳定性更好。GPS/BDS组合定位的定位精度也明显优于单一系统,这对GNSS高精度导航定位具有重要的参考价值。     

GPS Aided Inertial Navigation

The Global Positioning System is an extremely accurate satellite-based navigation system which, after its completion in 1989, will provide users worldwide, 24 hour. all weather coverage. A joint research project among Boeing, Rockwell-Collins, and Northrop has been completed in which a GPS receiver was integrated with a low-cost strap-down inertial navigation system and a flight computer. A Kalman filter in the latter allows in-fight alignment and calibration of the INS. In addition, feedback from the INS to the GPS receiver improves the system's ability to reacquire satellite signals after outages. The resulting system combines the accuracy of GPS with the jamming immunity and autonomy of inertial navigation. System tests were conducted in which a Boeing owned T-33 jet aircraft was flown through known test pattern to align and calibrate the INS. Earlier tests, including tests against an airborne jammer, were conducted in a modified passenger bus.     

Prototype personal navigation system

Honeywell Laboratories recently funded the development of a prototype personal navigation system based on MEMS technologies. The system components include a MEMS inertial measurement unit, a three-axis magnetometer, a barometric pressure sensor, and a SAASM GPS receiver. The system also uses Honeywell's human motion-based pedometry algorithm. The navigation process is based on a strap-down inertial navigator aided by feedback from a Kalman filter using typical measurements from the GPS, magnetometer and barometer when available. A key innovation is the addition of an independent measurement of distance traveled based on the use of a human motion algorithm. The navigation system combines the best features of dead reckoning and inertial navigation, resulting in positioning performance exceeding that achieved with either method alone. Subsequent to the Honeywell effort, DARPA funded an individual Personal Inertial Navigation System (iPINS) seedling program. Honeywell worked to improve the baseline personal navigation system with the objective of demonstrating the feasibility of reliably achieving navigation accuracy < 1 % of distance traveled in GPS-denied scenarios. In addition, an analysis was conducted to determine the benefit of incorporating terrain correlation into the personal navigation system. The results of this analysis indicate that overall navigation accuracy can be significantly improved through the application of terrain correlation. This presents an are presented. In addition, conclusions from the terrain correlation analysis conducted under the iPINS seedling program are included.     

Spacecraft orbit determination using GPS navigation solutions

The orbit determination using the GPS navigation solutions for the KOMPSAT-1 spacecraft has been studied. The Cowell method of special perturbation theories was employed to develop a precision orbit propagation, and the perturbations due to geopotential, the gravity of the Sun and the Moon, solid Earth tides, ocean tides, the Earth's dynamic polar motion, solar radiation pressure, and atmospheric drag were modeled. Specifically, the satellite box-wing macro model was applied to minimize the drag errors at low altitude. The estimation scheme consisted of an extended Kalman filter and Bayesian least square method. To investigate the applicability of the method to the KOMPSAT-1 spacecraft, the orbit determination was accomplished using the GPS navigation solutions for the TOPEX/POSEIDON and TAOS satellites. The orbit determination results were compared with NASA POE generated by global laser tracking. The position and velocity accuracy was estimated about 16∼7 m and 0.0157∼0.0074 m·s⁻¹ RMS, respectively, for the two satellites in the presence of SA. These results verify that an orbit determination scheme using GPS navigation solutions can provide the static orbit information and reduce conspicuously the position and velocity errors of navigation solutions. It can be suggested that the sequential and batch orbit determination using the GPS navigation solutions be the most appropriate method in the KOMPSAT-1 type mission.     

基于嵌入式平台的MEMS/GPS 组合导航系统实现研究

主要研究基于PC104平台的MEMS/GPS组合导航系统硬件实现方法.首先设计了对MTi-30 MEMS器件与GPS接收机的数据采集软件,基于统计分析方法分析建立了传感器的误差模型参数,构建了MEMS/GPS组合算法模型,基于MEMS惯性器件和GPS接收机实测数据确定了Kalman滤波器的系统噪声阵及量测噪声阵模型参数;然后利用实际测量数据进行了MEMS/GPS组合系统导航性能仿真;最后基于PC 104嵌入式平台,构建了MEMS/GPS组合导航系统原理样机,分别在静态和动态情况下完成MEMS/GPS组合导航算法实时测试,导航结果验证了硬件平台及导航算法的正确性.     

Road profile recognition for autonomous car navigation and Navstar GPS support

We discuss autonomous car navigation based on updating dead reckoning (DR) by road profile recognition (RPR). The navigation system requires sensors to detect changes in altitude and driving direction which are installed in modern cars for different purposes (e.g. ABS sensors). The layout of the navigation system is discussed and simulations are carried out over driving distances of approximately 150 km on the basis of realistic road data and ordinary sensor accuracies. Positioning errors of lower than 10 m (standard deviation) are observed. To achieve this accuracy the synchronization error between measured and mapped data must be continually estimated. The introduced navigation method is ideal to complete present commercial car navigation systems using Navstar GPS.     

On-line Vehicle Motion Estimation from Visual Terrain Information Part II: Ground Velocity and Position Estimation

An algorithm, combining velocity/height estimates, obtained from an airborne body fixed image shift estimator with auxiliary on-board measurements and sparsely stored terrain profile information constitutes an entirely passive autonomous navigation system suitable for moderate-g flight missions. Two versions are addressed. The "naive estimator," in which altitude estimates are multiplied by velocity/height estimaters, yields ground velocity. Position, obtained by integration, diverges with time. The "extended Kalman filter" (EKF) version, in which velocity and position are defined as state space components, locks on the stored terrain profile and does not diverge with time. It degenerates into the "naive estimator" if the terrain is completely flat. Numerical examples indicate excellent performance potential of the EKF estimator.     

卡尔曼滤波在弹道组合导航仿真中的应用

根据捷联惯性导航(INS)和GPS导航两个系统不同的特点,通过卡尔曼滤波方法实现了INS/GPS组合导航,以速度差和位置差作为卡尔曼滤波的量测量信息,建立了组合导航的简化滤波方程.在实际陀螺器件含有零偏的情况下,通过在角速度上引入定量的零位偏置来进行弹体模拟投放过程.将仿真导航结果和弹道参数比较,引入的陀螺偏置引起姿态角误差,而速度误差和位置误差比较小,导航计算参数误差在允许范围之内.     

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.     

Microwave Radiometric Sensing for Air Navigation

This paper discusses the results of an analytic study of the feasibility of using microwave radiometry as a technique for navigation data sensing in Army aircraft. The study included a review of Army aircraft characteristics and navigation requirements. Various means of sensing passively aircraft velocity, altitude, and velocity-altitude ratio were considered. While there appears to be no practical method for direct measurement of either velocity or altitude separately, it does appear possible to measure velocity-altitude ratio by comparing radiometric signals received from the terrain along the aircraft ground track. When combined with a radar altimeter, such a sensor could yield navigation data compatible with Army aircraft requirements. Microwave radiometry may also be the basis for direction sensing (to known landmarks) in high-flying aircraft or satellites.     

Blind GPS receiver with a modified despreader for interference suppression

The global positioning system (GPS) was designed to provide location estimates for various civilian and military applications using at least four satellites. Since GPS signals have a low signal-to-noise ratio (SNR), they also have a low signal-to-jammer ratio so that the accuracy of location estimates is influenced by cochannel interference and intentional jammers. We propose a low-complexity blind adaptive receiver that is based on a novel modified despreader and the constant modulus (CM) array. This system is capable of ing directional interference and capturing the GPS signal of interest without requiring explicit angle-of-arrival (AOA) information. We also consider the multiple satellite problem and extend the proposed receiver to capture several GPS signals of interest. Representative computer simulation examples are presented to illustrate the performance of the multicomponent system for the suppression of different jammer types.     

GPS自动归航系统在变化风场中的轨迹

研究全球卫星定位系统（GPS）自动归航系统在恒定风场中归航轨迹的计算，探讨了系统能够达到预定目标点的条件，给出系统在几种风场中的轨迹图。为了进一步验证归航轨迹能否回到预定点，给出了系统的变化风场中的仿真算法，并通过对仿真结果的分析，提出在系统着陆期间利用GPS定位和测速数据实行逆风控制的方案。     

Urban area performance of GPS receiver with simultrac capability

The theory of operation, practical applications, and technical performance of a Global Positioning System (GPS) receiver designed for urban area use are presented. The receiver tracks as many as eight satellites, or all visible satellites, and uses the signals of the four best satellites to ascertain its location. If visibility of one satellite is blocked, one of the additional satellites can be used to provide continuous navigation. Component-level system design choices are shown to support superior automotive vehicle location performance, including optimum mobile communication with satellites and ground-based relays     

Adaptations of a comparison technique for terrain navigation

This paper deals with a terrain navigation technique based on the comparison of terrain height measurements with a reference map. The comparison can be either based on minimum absolute differences, minimum square differences or on cross correlations. This paper will give an introduction to these methods and state some important adaptations. The first adaptation increases the independence of the terrain navigation system by calculating the position hypothesis only based on previous position measurements and the strap-down velocity. The second adaptation uses a detailed search to increase the performance and the reliability of the terrain navigation system. Both adaptations are important steps to a higher integrity of modular terrain navigation systems.     

Analysis of upgraded GPS internal Kalman filter

GPS receivers with provisions for inertial navigation system (INS) aiding are designed with internal Kalman filters that model generic INSs and process the basic GPS pseudorange and deltarange (range-rate) data to produce an output of inertially-smoothed, “GPS-derived” position and velocity. These Kalman filters model only the basic nine INS errors (position, velocity, and tilt) and do not model any INS gyro or accelerometer errors. It was found that a significant performance improvement could be achieved under conditions of degraded GPS satellite availability by augmenting this type of filter with the six INS gyro and accelerometer bias errors. It is, therefore, recommended that serious consideration be given to incorporating these states into the design of the GPS internal Kalman filter     

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)     

一种改进的地形轮廓预测匹配辅助导航算法

传统的地形轮廓匹配 (TERCOM )辅助导航系统 ,由于其实时性差 ,已不能满足飞行器超低空高速的导航需要。本文引入预测控制的思想 ,提出了一种基于高度特征的地形轮廓预测匹配方法 ,减少了计算量 ,提高了导航系统的实时性和机动性。