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Position Location and Navigation Symposium, 1994., IEEE

Date 11-15 April 1994

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Displaying Results 1 - 25 of 120
  • Proceedings of 1994 IEEE Position, Location and Navigation Symposium - PLANS'94

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    Freely Available from IEEE
  • Initial rapid alignment/calibration of a marine inertial navigation system

    Page(s): 348 - 354
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    Generally, the conventional strapdown marine inertial navigation system needs about 4 hours to settle the initial alignment/calibration under motion. The paper presents an effective approach of the initial rapid alignment/calibration on a strapdown marine inertial navigation system with three fiber optic gyros and three conventional accelerometers. In this approach, a modified least square filter, which implements a pre-filtering scheme of the measured signal disturbed by the ship's motion, is used to improve the accuracy and settling time of alignment/calibration. The accuracy and the settling time in this system are limited by the performance of a modified least square filter of the measured signal. The authors confirmed the validity of this approach to improve greatly the accuracy and the settling time from simulation results.<> View full abstract»

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  • GPS...more than a real world digitizer

    Page(s): 381 - 387
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    The Global Positioning System (GPS) has been with us now for over a decade, providing positioning information across a broad range of applications. In the geographical information systems (GIS) area, the potential of GPS technology is really only just starting to be realised. The major areas of use have been for mapping the locations of features, particularly for asset management. This paper describes a few of the issues involved in using the Global Positioning System to acquire data for GIS. This paper also describes one of the technology integration projects currently being undertaken at the School of Surveying, that explores the potential of integrated technologies for space-time monitoring of any phenomena. A prototype DGPS/GIS system was developed using lightweight, inexpensive, off-the shelf parts. The development of this type of technology promises to revolutionise the way one can acquire space-time data, providing us with an expanded vision of how to monitor the environment and manage all types of assets View full abstract»

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  • RTCA SC-159 Wide Area Integrity Broadcast/Wide Area Differential GPS status

    Page(s): 613 - 620
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    The Wide Area Integrity Broadcast (WIB) (formerly the GPS Integrity Channel-GIC) will use a network of ground stations at known locations to determine the status of every GPS satellite in view. It will then broadcast satellite health to GPS users in real time from a geostationary satellite (GS), thus providing system integrity. This broadcast will also include error estimates for the same GPS satellites that are valid over a specified region, which may include one or more countries or continents. These estimates, if accurate enough, can be used as differential corrections. This concept is called Wide Area Differential GPS (WDGPS). In addition, the broadcast signal will be modulated with a pseudo random noise (PRN) code that is synchronized with GPS time. Thus, it can also be used for ranging to augment the GPS system, thus improving system availability and continuity View full abstract»

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  • GNSS-progress towards implementation

    Page(s): 23 - 30
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    Global navigation satellite systems comprising the Navstar GPS and GLONASS systems and to be supplemented by an Inmarsat-3 overlay, will soon be operational. Full Operational Capability (FOC) for GPS can be expected early in 1995. For GLONASS progress towards FOC will be slower with a final completion date probably nearer 1996-98. Particularly in view of the interest in joint GPS/GLONASS initiatives, the progress of both systems towards a full operational complement deserves constant attention View full abstract»

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  • The application of spread spectrum datalinks to GPS-based air traffic navigation, surveillance, and control

    Page(s): 194 - 198
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    A spread spectrum datalink is considered as a potential candidate for support of DGPS-based navigation, surveillance, and control. Spread spectrum communications is a technology that for years has been exploited in military communications because it could provide the desirable characteristics of either immunity from intentional jamming or low probability of interception. More recently, the technology has been applied to civil communications because the same properties that result in those characteristics also provide for an efficient mechanism for multiple users to simultaneously share a band of frequencies on a noninterfering basis. The paper provides a brief review of the basic concepts of spread spectrum communications. That information is then used to support a discussion of the rationale for considering spread spectrum techniques in this air traffic control application. The advantages and disadvantages relative to alternative approaches are presented; and, the most appropriate spread spectrum designs in terms of both signal architecture and hardware implementation are discussed. The paper describes an effort underway at Harris Air Traffic Control Systems Division on a FAA contract. The program goal is to demonstrate a spread spectrum datalink in support of a GPS-based airport surface traffic management system. It is believed that it will result in the first ever demonstration of a spread spectrum datalink being utilized at an airport to help solve a real air traffic control problem View full abstract»

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  • A GPS integrity channel based fault detection and exclusion algorithm using maximum solution separation

    Page(s): 747 - 754
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    The paper presents a new GPS integrity channel (GIC) based fault detection and exclusion (GFDE) algorithm. The algorithm employs the maximum solution separation technique augmented by data broadcast over the GIC to ensure GPS integrity. Furthermore, GFDE improves on current snapshot RAIM techniques by reducing the effect of the accuracy and availability trade-off, thereby increasing system availability. After a brief description of the algorithm., the expected performance of GFDE is analyzed. Simulation results are presented which show availability that approaches the 0.99999 level required for sole means navigation for the enroute, terminal, and non-precision approach phases of flight over the conterminous United States ((CONUS) View full abstract»

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  • Analysis of the use of digital road maps in vehicle navigation

    Page(s): 494 - 501
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    Digital road maps are being used increasingly throughout the world as they become more available. Five major digital road map suppliers are focusing their efforts on producing databases that support vehicle navigation functions. Of a total of 147 vehicle navigation systems in the world, 89 use in-vehicle maps, of which, 35 employ map matching, and 31 offer real-time route guidance. Vehicle navigation systems are limited by the maps they use, so the availability of inexpensive, complete and seamless navigable digital road maps remains as an impediment to the wider use of vehicle navigation systems View full abstract»

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  • Performance analysis of a shipborne gyrocompass with a multi-antenna GPS system

    Page(s): 337 - 343
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    A four-receiver configuration was used to estimate the three attitude parameters and assess the headings obtained with a Sperry Mark 3 Model C gyrocompass mounted on a 1500 tonnes, 72-m vessel. The GPS configuration consisted of four 10-channel NovAtel GPSCards operating in independent mode. The antenna separations varied between 5 and 15 m. The antenna locations in the ship coordinate system were obtained through a combination of a conventional and GPS survey. The remaining misalignment between the gyrocompass and the multi-receiver configuration was estimated by comparing GPS and gyrocompass heading measurements made throughout the sea trial. The formulation used to estimate the above attitude parameters is described. The multi-receiver data was processed with The University of Calgary's MULTINAV attitude software. The performance of the gyrocompass was assessed using 10 hours of data collected over a two-day period in Spring 1993 under a wide range of ship manoeuvres such as acceleration, deceleration and 360° turns. The estimated double difference carrier phase residuals, which provide a measure of receiver carrier phase noise and multipath, were below the 5 mm level. The estimated accuracy of the GPS-derived heading parameter was 2.2 arcmins or 0.04° and the standard deviation of the differences between GPS and gyrocompass headings during straight trajectory segments was 0.16°. The use of a two-receiver configuration to determine the heading component was shown to deliver a level of accuracy similar to that obtained with the four-receiver configuration View full abstract»

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  • GDOP and the Cramer-Rao bound

    Page(s): 663 - 668
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    The GDOP is frequently thought of as a number signifying the effect of satellite geometry on computed position. More generally, it is well known that the GDOP matrix is the covariance of the linearized least squares errors in estimating position and bias from pseudoranges with unit variances. However a much stronger statistical interpretation is possible. In this paper we explore the relationship between the GDOP matrix and the Cramer-Rao bound of classical statistical point estimation. We also detail an interpretation of GDOP made in earlier work. In the first part of the paper we show that the GDOP matrix is actually the Cramer-Rao lower bound on estimates of position and bias given that the pseudorange errors are Gaussian distributed. In light of recent work indicating that pseudoranges not affected by SA are likely not Gaussian, we discuss generalization of this result to symmetric non-Gaussian pseudorange errors. In the second part of the paper, the GDOP is interpreted in terms of covariance about the average line of sight vector. This interpretation is used to compare ranging systems with pseudoranging systems. It is demonstrated that ranging systems are inherently more accurate, given the same geometry and measurement variances. Conditions under which the two systems are equivalent are derived. The role of the clock bias in this relationship is detailed View full abstract»

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  • Application of on-the-fly kinematic GPS to seismic surveying

    Page(s): 555 - 561
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    The application of on-the-fly kinematic GPS (OTF-KGPS) to establishing a large scale seismic survey control is pioneered. The seismic points are staked out in the field using the real-time DGPS method and their precise coordinates are determined using OTF-KGPS. The paper briefly describes land seismic survey requirements. It then outlines the key concepts of the employed method of OTF-KGPS. Field surveys are described and sample results are given View full abstract»

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  • Quality control in DGPS separation vector systems

    Page(s): 726 - 732
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    Quality control and the computation of relative positions of multiple remote objects are key elements of a marine seismic streamer tracking system. NCS International and Pulsearch Navigation Systems have developed a separation vector system that has undergone extensive testing in the Gulf of Mexico and the North Sea. Each remote object, or in this case a tail buoy, is equipped with a controller board, GPS receiver and radio modem. Raw GPS measurements are collected and transmitted to the vessel where they are processed and stored on an IBM compatible computer using a Windows operating system. Differential GPS corrections are received by the vessel and used in the real-time vessel solution, if available. Processing includes using a series of eight-state Kalman filters for position and velocity determination for the vessel and each buoy. The detection and identification of measurement blunders are performed along with the computation of precision estimates in the form of confidence regions. Reliability measures are computed in real-time giving a measure of the strength of the solution. With these latter estimates, the computed positions are said to be repeatable when reliability measures lie within the precision confidence regions. The paper describes the variety of textual and graphical display screens available for the operator, including items such as range residuals, range corrections, satellite constellation information, quality assurance parameters and statistics on communications. The hardware for the system and the method of operation is described. Experience to date with the system is highlighted View full abstract»

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  • Role of land navigation in a vehicular hazard warning system

    Page(s): 502 - 511
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    The In-Vehicle Safety Advisory and Warning System is a Federal Highway Administration program to develop a nationwide vehicular information system that provides drivers with advance, supplemental notification of dangerous road conditions using electronic warning zones with precise areas of coverage. The goal is to ameliorate the severity of scenarios which are particularly hazardous and have remained hazardous despite traditional crash reduction techniques such as mechanical signing. This system provides additional safety by enhancing the real time interaction between the general driving public and professional agencies. While appropriate for both urban and rural settings, the primary focus of IVSAWS is the rural transportation environment View full abstract»

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  • Dynamic Environment Communications Analysis Testbed (DECAT) and its applications to Space Shuttle Orbiter and Space Station usage of the Global Positioning System (GPS)

    Page(s): 8 - 15
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    The Communication System Simulation Laboratory (CSSL) provides a facility for analyzing and simulating space communication systems. The CSSL has simulation tools that model NASA communication systems and the environment in which they operate. One of these tools is a radio frequency coverage analysis tool called the Dynamic Environment Communications Analysis Testbed (DECAT). DECAT provides the capabilities to model the orbital and structural dynamics of space vehicles and to incorporate user-written control functions to calculate such values as the occurrence of planetary or structural blockage. DECAT can analyze a space vehicle's usage of the Global Positioning System (GPS) from a communication link point of view by using control functions to calculate which GPS space vehicles (SVs) are available based on Earth blockage, structural blockage, vehicle antenna pattern, and signal margin. DECAT also contains control functions to calculate the geometric dilution of precision (GDOP) and position dilution of precision (PDOP) given combinations of available SVs. The paper focuses on DECAT simulations of Space Shuttle Orbiter and Space Station usage of GPS. For Space Shuttle mission 51, DECAT was used to investigate usage of GPS for relative positioning for both the Space Shuttle and the Orbiting and Retrievable Far and Extreme Ultraviolet Spectrometer (ORFEUS) Shuttle Pallet Satellite (SPAS). How often the Space Shuttle can receive four GPS SVs and how often the Space Shuttle and SPAS select the same four SVs for solution were investigated. For the Space Station, DECAT was used to investigate GPS coverage View full abstract»

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  • GPS, 3-D maps and ADS provide a seamless airport control and management environment

    Page(s): 689 - 696
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    This paper describes DSDC's GNSS based airport control and management system and research conducted at the Manchester, New Hampshire airport. The system was demonstrated to the FAA in August of 1993 while under a BAA demonstration contract. The system utilized new concepts and techniques which are compatible with GNSS based navigation and positioning information. Major system operational elements and a system level processing overview are presented View full abstract»

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  • DGPS positioning using carrier phase for precision navigation

    Page(s): 410 - 417
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    DGPS with carrier smoothed code is employed widely in real time applications. Its accuracy level can satisfy the ICAO-CAT-I and CAT-II landing requirements according to the authors experiences. The investigation in the paper shows potential possibility and conditions to use this technique for the accuracy requirement of CAT-III. For accuracy improvement, DGPS with only carrier phase measurement is needed. However, in navigation integer ambiguities of carrier phase measurement must be resolved during flight. The paper presents a triple difference technique for six unknowns, The phase ambiguities, instead of being resolved, are eliminated by triple differencing, The six coordinates of the mobile receiver at two epochs are the unknowns to be determinated in real time. The combined GPS/GLONASS system will ultimately provide a simultaneous availability to receive eight or more satellites. With seven or more observable satellites one can get an analytical resolution of position without static initialization or any searching technique for ambiguities. It is also possible to achieve an analytical solution with GPS alone by using two reference stations. From each reference/mobile station combination at least three triple difference equations can be obtained so that six independent equations together are sufficient to also resolve six unknowns. The initial results of this technique are presented View full abstract»

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  • Performance analysis of a narrow correlator spacing receiver for precise static GPS positioning

    Page(s): 355 - 360
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    The performance of narrow correlator spacing C/A code GPS receiver technology was assessed for static GPS surveying using 10-channel, single frequency GPSCard receivers. A series of surveys was conducted in the Eastern United States in December 1992 in support of this assessment. Baselines of 0.5 to 320 km were observed over several days to analyse repeatability and agreement with reference coordinates. The carrier phase measurements were post-processed using double and triple difference approaches. Precise orbits were used to isolate the atmospheric and receiver error sources. The effect of multipath on carrier phase measurements is demonstrated. In order to determine the effect of the ionosphere on long baseline (>200 km) solutions, the ionospheric effect was estimated using a single frequency code/carrier phase divergence approach. This method is particularly well suited in this case in view of the high C/A code accuracy of the GPSCard. The effect of the ionosphere on the baselines was found to reach several ppm. The repeatability of the baselines varies between 1.2 and 3.0 ppm. The agreement of the reference coordinates with the L1 baseline solutions is 3.7 ppm while that with the ionospherically corrected long baseline solutions is 1.1 ppm View full abstract»

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  • A new method for fast carrier phase ambiguity estimation

    Page(s): 562 - 573
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    The Global Positioning System (GPS) double-difference carrier phase data are biased by an integer number of cycles. A new and successful method has been developed and demonstrated that enables very fast integer ambiguity estimation. The method makes use of an ambiguity reparametrization that allows one to reformulate the original ambiguity estimation problem into a new problem that becomes much easier to solve. The theoretical concepts of the method are presented, and some representative numerical results are given and discussed. In particular, it is demonstrated that a very significant reduction in both the correlation between the ambiguities and in the elongation of the corresponding confidence ellipsoid can be reached. Typically a reduction by a factor of between 102 and 103 of the square-root of the condition number of the confidence ellipsoid can be obtained. Also the gain in time, which is needed to follow through the various computational steps, is demonstrated View full abstract»

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  • Modified strapdown inertial navigator error models

    Page(s): 426 - 430
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    The paper revisits the problem of error modeling for strapdown INS for the purpose of navigation sensor blending with a Kalman filter. This problem has been addressed repeatedly over the last 30 years, and different perspectives on INS error modeling have emerged. The paper reviews these, focussing in particular on the properties and relative advantages and disadvantages of the φ-angle and ψ-angle error models. The paper then addresses some new concepts for the design of a Kalman filter model for integrated navigation. The sometimes troublesome problem of the explicit occurrence of the specific force in both error models is averted with the modified φ-angle and ψ-angle error models proposed in the paper, in which the explicit representation of the specific force is canceled via a transformation of the velocity error states View full abstract»

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  • Digital L-band receiver architecture with direct RF sampling

    Page(s): 209 - 216
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    This paper describes the architecture of a fully digital receiver well suited for Global Positioning System (GPS) satellite radio-navigation and other spread-spectrum applications. The unique design of this receiver allows phase coherent measurements to be made across a broad range of frequencies, enabling optimal combination of a set of measurements from signals on different frequencies, for example GPS L1, L2, and L3, GLONASS or ground-based pseudolites. The receiver methodology provides precise absolute positioning measurements by maintaining phase coherency between frequencies of interest by direct L-band digital sampling. A one-bit sampler head is discussed that is suitable for navigation and digital communications applications. Surveillance applications can be accommodated with an expanded, multi-bit sampler. The design is particularly suited for chip set integration leading to a miniaturized and low cost receiver. Design of the receiver's digital front-end provides coherency between the code and carrier phase of the measurements across a 400 MHz bandwidth with down-conversion effected by digital techniques. In addition, it features a software configurable topology that enables filter parameters to be loaded dynamically, allowing rapid change of tracking frequency. The flexible “software receiver” architecture has been developed to allow the receiver to be dynamically reconfigured for different applications. This allows the receiver channels to be used for GPS navigation, ionospheric calibration, attitude determination, or even GLONASS navigation simply through software commands. Sampler performance criteria are discussed as well as test data demonstrating the effect of sampler performance on the receiver correlation loss View full abstract»

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  • A GPS attitude error model for Kalman filtering

    Page(s): 329 - 336
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    Sea trial data from two attitude measuring GPS receivers has been analyzed, using high quality inertial attitude for reference. Since this type of GPS measurement could potentially provide rapid and precise attitude at a much lower cost than the inertial equipment normally used, it is of considerable interest. This paper provides some background on GPS attitude technology, presents the attitude errors observed during these sea trials and characterizes these errors as linear stochastic processes, suitable for use in a Kalman filter for sensor integration View full abstract»

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  • Test results over extended environments for Litton's inertial navigation grade interferometric fiber optic gyro

    Page(s): 176 - 181
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    Litton's Guidance and Control Systems Division has been developing interferometric fiber optic gyro (IFOG) technology for inertial navigation applications (requiring bias ⩽0.01 degrees per hour, one sigma) since 1986. The objective of this effort has been to develop a small, lightweight, highly reliable rotation sensor based on solid-state technology for productionization before the year 2000. A number of applications of this technology are currently in development. This paper focuses on the testing status of Litton's LN-250 IFOG which incorporates one kilometer of fiber in a package less than three inches in diameter. Results from tests over extended environments show that inertial navigation grade performance in bias, angular random walk, scale factor and input axis alignment has been achieved under static and dynamic conditions. Plans for further development and testing are discussed View full abstract»

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  • Vertical polarization-VORTAC'S last weak link

    Page(s): 84 - 90
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    This paper discusses a problem with the VHF Omnirange System (VOR) which prevents it from performing to its full potential. Some courses on many stations have an unnecessary amount of error plus roughness and scalloping which differs with each aircraft and in each location that it is received. The majority of these effects are not caused directly by reflecting objects as commonly believed. The cause, vertical polarization, and method of correction have been known for many years, but unfortunately have not been properly recognized or universally applied. Tests and corrections should be accomplished in order that those who wish to continue to use the VOR in what is probably its last ten to fifteen years, are provided the best available short distance navigation service without the expense of installing additional equipment in their aircraft View full abstract»

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  • The next generation marine inertial navigator is here now

    Page(s): 121 - 127
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    The MARLIN (Marine Ring Laser Inertial Navigator) development program has matured into the MK 49 Ship's Inertial Navigation System (SINS). The MK 49 system is in full production with proven at-sea performance better than NATO SINS specifications. Production is currently underway for 56 NATO SINS systems for the navies of The Netherlands, Spain, and the United Kingdom and for 20 MK 49 Inertial Navigators for the navies of Australia and New Zealand. Thirty-one systems have been delivered to date (November 1993) after passing a factory acceptance test (FAT) involving 30 hour NATO 1, NATO 2, and NATO 3 scenarios with full Scorsby motions and heading changes every six hours. Ten systems are operational aboard NATO ships. Formal shipboard acceptance tests (SATS) have been performed successfully. The SATS involved zig-zag maneuvers, speed changes, and heading change box tests in the North Sea, all of which were passed with significantly better performance than NATO SINS specifications. The authors discuss the advantages of the MK 49 SINS and present performance results View full abstract»

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  • Determining GPS anti-jamming performance on tactical missiles

    Page(s): 641 - 648
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    The use of the Global Positioning System (GPS) for aiding the navigation of missiles in a tactical environment is growing. Two missile systems which have fielded GPS are the Tomahawk Cruise Missile and the Standoff Land Attack Missile (SLAM). Other systems such as the Army Tactical Missile System (ATACMS) are incorporating GPS into their navigation solution. When integrating GPS into a vehicle, the designer has to determine the specifications of the receiver that will meet the system objectives. One of these specifications will be the amount of jammer-to-signal (J/S) power the receiver and antenna system can withstand without losing track of the satellites. To aid in determining this requirement two simulation tools, VISJAM and VISCON, were developed to measure the performance of the GPS user equipment in a jamming environment. Both of the tools use an externally generated vehicle trajectory and a user supplied almanac to calculate the vehicle to satellite geometry. VISJAM determines the number of visible satellites, the optimum set of satellites to track, the corresponding geometric dilution of precision (GDOP), the J/S for each satellite, and the acquisition state for each satellite (State 3 or State 5) at each time step for multiple jammers. VISCON calculates a contour map showing the minimum required jamming power at each point on the map that will deny the GPS function to the missile. The resolution of the contour map is user definable View full abstract»

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