A Prototype System for Navigation in GPS-Challenged Environments By Chris Rizos, Dorota A. Grejner-Brzezinska, Charles K. Toth, Andrew G. Dempster, Yong Li, Nonie Politi, Joel Barnes, Hongxing Sun, and Leilei Li A team of Australian and U.S. researchers have integrated a ground-based system with GPS and INS to create a hybrid system that provides precise and accurate position information continuously in a variety of environments where GPS alone comes up short. INNOVATION INSIGHTS by Richard Langley GPS HAS ITS LIMITATIONS. Although it is a 24/7 global system, it doesn’t work everywhere. The microwave radio signals transmitted by the satellites are rather weak, and although they can provide excellent positioning performance when a receiver’s antenna has a direct line-of-sight view of a sufficient number of satellites well spread out in the sky, positioning accuracy degrades or becomes impossible when the signals are effectively blocked by obstacles such as trees, rock faces, and buildings outdoors and by roofs, ceilings, and walls indoors. In many obstructed environments, the signals aren’t completely blocked but rather their power is severely attenuated so that they are no longer strong enough to be acquired and tracked by a conventional GPS receiver. Remarkable progress has been made in the development of super-sensitive receivers that, in conjunction with an appropriate antenna and assistance information provided over a mobile phone network, can provide position fixes in such environments. However, the precisions and accuracies of these pseudorange-based positions are often very poor — perhaps as low as 100 meters or more. So, is it possible to obtain precise and accurate positions in obstructed environments? Well, we could add measurements from GLONASS (or other satellites) to GPS measurements, but GLONASS suffers the same problem as GPS, and while the additional satellites could be an advantage in some partially obscured areas there are many places where we won’t be any better off. We could use an inertial navigation system (INS), but such devices have their own weaknesses such as the requirement of initial calibration and the accumulation of position error with time. Are there any other technologies available? We know GPS works very well when there is a direct line-of-sight view between the satellite transmitters and the receivers and carrier-phase measurements can provide decimeter- and even centimeter-accuracies. So why not develop a ground-based system that works in a similar way to GPS, which would allow you to place the transmitters wherever you like? Well, such a system has indeed been developed and in this month’s column, a team of Australian and U.S. researchers describes how they integrated the ground-based system together with GPS and INS to create a hybrid system that provides precise and accurate position information continuously in a variety of environments where GPS alone comes up short. “Innovation” features discussions about advances in GPS technology, its applications, and the fundamentals of GPS positioning. The column is coordinated by Richard Langley, Department of Geodesy and Geomatics Engineering, University of New Brunswick. The determination of the position and orientation (or “pointing direction”) of a device (or platform to which it is attached), to high accuracy, in all outdoor environments, using reliable and cost-effective technologies is something of a “holy grail” quest for navigation researchers and engineers. However, ongoing research has identified two classes of applications that place stringent demands on the positioning/orientation device: (a) man-portable mapping and imaging systems that operate in a range of difficult urban and rural environments, often used for the detection of underground utility assets (such as pipelines, cables, conduits), unexploded ordnances and buried objects, and (b) the guidance/control of construction or mining equipment in environments where good “sky view” is not guaranteed. The solution to this positioning/orientation problem is increasingly seen as being based on an integration of several technologies: satellite (GNSS including GPS) and terrestrial ranging systems, inertial navigation systems (INSs), laser guidance/scanning systems, and even electro-optical devices such as surveyors’ total stations or laser scanners. Each has its shortcomings, but within an integrated system, advantage can be taken of the complementary characteristics of several of these sensor technologies. Centimeter-level accuracy positioning systems for outdoor use typically have at their core the GPS technology. GPS is, in fact, the most effective general-purpose navigation tool ever developed because of its ability to address a wide variety of applications: air, sea, land, and space navigation; precise timing; geodesy; surveying and mapping; machine guidance/control; military and emergency services operations; hiking and other leisure activities; personal location; and location-based services. The varied applications use different and appropriate receiver instrumentation, operational procedures, and data processing techniques. But all require signal availability from a minimum of four GPS satellites for three-dimensional fixes. However, one of the usual limiting factors in using GPS is the need for direct line-of-sight between the satellites and the ground receiver. In particular, the robustness of positioning is compromised when GPS receivers are near or under trees, in urban/suburban areas, or in deep open-pit mines and construction sites, where there is partial sky view obstruction by buildings or walls. The traditional means of overcoming the gaps in navigation coverage due to satellite signal blockages is to use an INS. An INS (with its inertial measurement unit or IMU) is also the most convenient means of determining the orientation of the device or platform. The integration of GPS and INS can, in principle, overcome the defects of standalone INS (sensor errors that grow unbounded with time) and GPS (signal availability requirement). But navigation accuracy degrades rapidly if there are no GPS measurements to calibrate the INS sensor errors. A new terrestrial RF-based distance measurement technology offers promise of continuous signal coverage, even in difficult urban/rural environments. This technology is known as “Locata.” The Locata approach is to deploy a network of ground-based transceivers that cover an area with strong time-synchronized ranging signals. When a Locata receiver uses four or more ranging signals it can compute a high-accuracy position entirely independent of GPS or INS. However, a standalone Locata receiver has its own shortcomings: (a) in some situations it may be difficult to achieve good vertical dilution of precision due to logistical constraints of placing transmitters (to give a variation in elevation angle between the terrestrial transmitters and the receiver whose positions are to be determined), and (b) as with GPS, multiple receivers/antennas are required to derive orientation information. What is therefore required is several carefully selected navigation sensor technologies, integrated within a single hardware package, the measurements from which are simultaneously processed to provide continuous, reliable, and accurate navigation solutions (that is, both position and orientation information). In cooperation with Locata Corporation, the SNAP Laboratory within the School of Surveying and Spatial Information Systems at the University of New South Wales (UNSW) and the SPIN Laboratory at The Ohio State University have assembled a working prototype of a hybrid system based on GPS, inertial navigation, and Locata receiver technology to provide seamless and reliable navigation aimed at supporting vehicle guidance and control, open-pit mining, mobile and GIS mapping, and industrial applications. Locata Technology The SNAP Lab has been conducting pseudolite research for many years, and has experimented with pseudolites in nonsynchronous and synchronized modes for a variety of applications, using both the GPS L1 frequency as well as the 2.4 GHz ISM band frequencies. Locata Corporation has developed state-of-the-art RF terrestrial positioning technology (“Locata”), which consists of a network (“LocataNet”) of time-synchronized pseudolite-like transceivers (“LocataLites”). UNSW has assisted in the development of the technology through experimental testing and benchmarking. In a relatively open outdoor environment, the LocataNet can provide real-time stand-alone kinematic positioning (without a base station) at centimeter-level accuracy. Even in an indoor environment where LocataLite signals arrive at a Locata receiver via non-line-of-sight paths (penetrating the walls of buildings), the static positioning quality can be at the sub-centimeter level, and also at the sub-meter level for kinematic positioning. Locata has several advanced features that have been developed over a period of about 10 years through several technology generations, including a time-synchronized positioning network, network propagation to many LocataLites, improved signal penetration, change of transmitting frequency and signal structure, and spatial and frequency diversity. In TABLE 1, the key characteristics of the two generations of Locata technology are listed. Using 2.4 GHz not only means the frequency is license-free, but also permits transceiver output power of up to 1 watt, which means greater operating distances (up to 10 kilometers). Using dual-frequency signals changes the initial phase-bias resolution from known-point initialization to on-the-fly (OTF), where the initial phase bias is resolved while the receiver is moving. The higher chipping rate (10 MHz) results in less pseudorange multipath error, because the delay in a reflected signal will rarely be more than two chips. The 10-Hz measurement rate allows relatively high velocities of the receiver. Table 1. Specification summary of Locata’s first- and second- generation systems. In terrestrial-based RF-based positioning, multipath error is more severe than with GPS, because the terrestrially transmitted signal arrives at the receiver at a very low (typically less than 10 degrees) or even a negative elevation angle, which can result in severe multipath signal fading. In the second-generation Locata system, spatial and frequency diversity techniques are employed. Spatial and frequency diversity are two of the three types of diversity principles (the other being polarization) that are common practices in terrestrial RF communications to mitigate against signal fading. The LocataLite transceiver uses two spatially separated (usually in the vertical) antennas, which transmit two signals at different frequencies. This gives a cluster of four diverse signals transmitted from one LocataLite. With this diversity technology, Locata kinematic positioning in moderately obstructed environments can provide centimeter-level quality with 100-percent coverage, as well as consistent geometry and high reliability. The Locata’s multipath mitigation technology is very important and relevant to this project, because the operational environments are often vegetated or wooded. Triple Integration As discussed in the preceding sections, there are both advantages and disadvantages to every navigation sensor. GPS and Locata have high positioning accuracy in open or moderately obstructed environments, but they are sensitive to signal blockage such as the case in dense forests, urban canyons, deep mine pits, and indoors. In contrast, INS is totally autonomous — that is, independent of external signal sources — and has high output rate for position, velocity, and attitude, but its unaided navigation error grows rapidly with time. The most common data-processing tool to integrate GPS and INS is the Kalman filter, which forms the basis for multi-sensor integration in this research. The basic Kalman filter applies to linear system models. Therefore, several variations were developed to cope with the non-linear navigation model, such as the extended Kalman filter and the unscented Kalman filter. The following discussion of the integration of the GPS/INS/Locata sensors is focused on two aspects: 1) the system state selection, and 2) the measurement model or integration model that decides which information to pass to the filter. The error state vector consists of a nine-dimensional navigation error state sub-vector (three for the position, three for the velocity, and three for the orientation), an accelerometer error state sub-vector, a gyroscope error state sub-vector, and a three-dimensional gravity disturbance state sub-vector. Of course, other sensor error models can be considered for the gyroscope and accelerometer sensors, such as a combination of random constants, first-order Gauss-Markov variables, scale factors, and so on. In this case, the state space could have a dimension of more than 30. The objective is to adjust the sensor error model later based on experimental results (if needed). However, because of the limitations of observability, it is not yet known whether an augmented error state vector would give better results. When integrating INS hardware with other sensors, the sensors cannot share the same physical location, which would be ideal from a theoretical point of view. Knowing the spatial relationship among the sensors is important to ensure the highest possible navigation performance. The displacement vectors or mounting biases are offsets, also referred to as lever arms, from the center of the IMU to the centers of the other sensors. These lever-arm parameters may be included in the Kalman filter and thus can be estimated. However, if the lever arms are precisely measured during the assembly of the system, they do not need to be included in the filter as estimable parameters. For multiple sensor integration in a Kalman filter, there are essentially two types of general models: loosely coupled and tightly coupled. The loosely-coupled model uses a decentralized filter that has several sub-filters to process the sub-systems independently. In other words, the Kalman filter solutions from the sub-systems are combined in an overall Kalman filter that provides the integrated navigation solution. In contrast, the tightly-coupled model uses a single main filter to process the output of all sensors. In GPS/INS integration, tightly-coupled systems have obvious advantages in environments where GPS signals are frequently lost, because they can rely on the other sensor(s) when GPS positioning becomes impossible. In the tightly-coupled model, the raw observations of all sensors will be input to the main filter. For GPS and Locata, the primary observations will be the carrier phase measurements, as code (pseudorange) observations cannot provide the required accuracy. High-accuracy GPS positioning needs to address the issue of carrier-phase ambiguity. The ambiguity can be treated as an unknown in the Kalman filter, but it may take several minutes to resolve the ambiguity using GPS alone. Using certain ambiguity resolution techniques, however, the ambiguity can be resolved outside the main filter in the GPS/INS high-precision (carrier-phase) integration filter. Note that if the ambiguity were to be resolved within the filter, this would increase the number of states of the filter. For the GPS component, ionospheric delay should be included for applications that cover a large area. Ionospheric delay can be resolved using network-based differential techniques, but it will affect the ambiguity resolution for single baseline differential positioning if it is not included in the local solution. The filter is designed either to use, or not to use, ionospheric delay, which can ensure flexibility to accommodate network-based and single-baseline differential positioning. As mentioned above, the measurement model in the tightly-coupled model is based on the raw observations. For GPS and Locata, the observations will be the carrier-phase observations. The approximate values for the linearization of the GPS and Locata measurement equations are provided by the INS navigation solution. The GPS carrier-phase ambiguity is solved independently outside the Kalman filter with OTF techniques. The GPS differential positioning coefficient matrix remains the same regardless of whether or not a network-based differential technique is used. For velocity determination, the double-differenced Doppler observation is used to eliminate the clock error rate as an unknown (because it is difficult to model this in the filter). The initial carrier-phase bias of the Locata is also not included in the filter, because it can be resolved instantaneously with dual-frequency data in the Locata second-generation system. The implementation of the filter will be flexible, so adjustments can be made to account for actual environmental conditions. The filter is designed with an open interface and is modular in structure, so that components can be added (or removed) from the model. In open-sky areas, GPS is sufficient for system positioning, so only its observations need to be processed. In moderately obstructed environments, GPS and Locata observations will be processed. In this case the number of GPS observation equations is limited and sometimes will be less than four. FIGURE 1 illustrates the flowchart of the triple-integration of GPS, INS, and Locata. Figure 1. Workflow of the integrated GPS/ INS/Locata system. Field Tests For experimental purposes, we used a dual INS, based on a navigation grade unit and a tactical grade unit. In addition, a Locata receiver and a dual-frequency GPS receiver were placed on a vehicle at Locata’s Numeralla Test Facility (NTF) near Canberra, Australia. This test site features both open-sky and obscured environments, allowing for testing the system’s performance under truly challenging scenarios. The test was repeated by mounting the devices on an autonomous electrical car, driven on the UNSW campus. In both cases, the separation between the rover and the terrestrial transmitters was between a few tens of meters to several kilometers. The GPS and Locata data were processed separately (for testing the internal consistency) as well in a hybrid solution, resulting in few-centimeter-level accuracy per coordinate, depending primarily on GPS availability and the geometry between the rover and Locata devices, as well as the level of multipath fading. Test 1: NTF. The first integration test was conducted at the NTF on March 17, 2008. The NTF covers an area of approximately three hundred acres (2.5 kilometers × 0.6 kilometers) and is ideally suited to real-world system testing over a wide area. At the NTF, a number of LocataNet configurations are possible through the installation of permanent antenna towers. The network configuration used for this experiment is illustrated in FIGURE 2. Figure 2. NTF: LocataLite network. Before the test, a special mounting platform was designed and built. The platform, shown in FIGURE 3, consists of a two-level metal frame. The bottom level can accommodate two inertial measurement units, while the top level can hold up to four antennas. The platform can be easily attached to either the roof of the NTF test vehicle or to the body of UNSW’s small electric car (described later). Figure 3. Devices setup for the NTF test. The devices used in the test include two dual-frequency GPS receivers (one used as the rover receiver and the other as the base station), one navigation grade INS, and one Locata rover unit. The GPS antenna and the Locata antenna were mounted with the INS together on the top of a truck. The GPS data rates were set to 1 Hz. The average length of the GPS differential baselines was about 1.2 kilometers. The GPS observation conditions were good during the testing period. The Locata data rate was set to 10 Hz, while INS data rate was 256 Hz, and both were synchronized with the GPS time using SNAP-Lab-developed time synchronization devices based on field-programmable gate array (FPGA) technology. The GPS/INS data were first processed in tightly-coupled mode. The trajectory is depicted in FIGURE 4. The standard deviation of position, velocity, and attitude are shown in FIGURES 5-7 respectively. Figure 4. The trajectory of the vehicle in the NTF test Figure 5. The standard deviation of position in the test. Figure 6. The standard deviation of velocity in the test. Figure 7. The standard deviation of attitude in the test. In Figures 5-7, it can be seen that the standard deviations of position and velocity are less than 0.02 meters and 0.01 meters per second respectively. The standard deviations of pitch and roll angles are less than 0.001 degrees as well as that of yaw, which is less than 0.01 degrees after the vehicle starts to move, at about the 1500th second. The Locata data was post-processed using Locata’s Integrated Navigation Engine (LINE). It provides an unsmoothed single point position using carrier-phase measurements. The initial ambiguity bias was resolved using the data from the GPS carrier-phase position. Following this initialization, the Locata solution was computed independently of GPS. A 15-meter tower LocataLite location in the vicinity of the start and end of the test (indicated by the “figure eight” pattern in FIGURE 8) allowed sufficient geometry for 3D positioning using Locata. For the rest of the data where there was insufficient vertical geometry, GPS height aiding was used. Figures 8 and 9 show the independent Locata and GPS solutions (without lever arm correction) for the section of the trajectory in the vicinity and the end of the test, respectively. The Locata solution compared to the GPS solution to within a few centimeters for the entire trajectory. Figure 8. Section of trajectory showing independent Locata solution (black) vs. GPS (blue) with no lever-arm correction. Figure 9. End of trajectory showing independent Locata solution (black) vs. GPS (blue) with no lever-arm correction. To test the GPS/INS/Locata integration, some GPS observation epochs were deleted to simulate two GPS blockages from seconds of week 94100 to 94250 and from 94500 to 94600. The INS standalone navigation errors with this deleted GPS data were about 8 meters and 2.6 meters, respectively. In the final GPS/INS/Locata integration test, Locata compensated for the missing GPS data. The integration result was almost identical to the GPS/INS integration result obtained with the original GPS observed data clearly showing that the Locata system could seamlessly replace GPS in this scenario. Test 2: Electric Car. Early in 2007, UNSW researchers established a permanent LocataNet on the university campus to provide a research and test facility at UNSW devoted to the Locata technology. The LocataNet setup at UNSW is illustrated in FIGURE 10. It consists of four dual-frequency LocataLites situated on tops of four buildings surrounding a lawn test area. The master LocataLite is on the Civil Engineering building and the other three LocataLites are synchronized to it. Figure 10. LocataLites on the UNSW campus. Currently, to be able to obtain a carrier-phase position solution with Locata, the initial ambiguities need to be resolved by initializing the rover receiver on a known position. For this purpose, a point in the middle of the test area was surveyed, and the coordinates were used to initialize the Locata receiver. SNAP Lab has developed a small electric car that can be driven using an attached handheld controller (see FIGURE 11). The controller enables the car to move in both forward and reverse and to steer the front wheels. Figure 11. The electronic car used in the test. For these tests, the same mounting platform as the one used in the previous experiment allowed all the sensors and ancillary equipment to be attached to the car. For this experiment, we used the following equipment: a Locata receiver, two GPS receivers, a tactical grade INS, a 360-degree prism (tracked by a robotic total station), and two time-sync FPGA data-logging devices. The starting position was the known point in the middle of the Locata network. The car was then driven in a circular path three times before finishing back at the starting position. During the test the raw data stream from the Locata receiver, the GPS receivers, and the INS were recorded using the time-sync data-logging devices. In addition, a robotic total station (RTS), which was set up at the edge of the test area, automatically tracked the prism position (the data was recorded internally). The Locata data was post-processed using LINE to give a single point unsmoothed carrier-phase solution. The initial ambiguity bias was resolved using the data from the GPS carrier-phase position. Following this initialization, the Locata solution was computed independently of GPS. Where there was insufficient vertical geometry (at the very west end of the trajectory shown in FIGURE 12), GPS height aiding was used. The Locata-only solution and the RTS result are shown in Figure 12. The two solutions compare to within a few centimeters of each other. Figure 12. The trajectory from the Locata-only and robotic total station solutions. We then carried out the integrated GPS/INS processing. To test the GPS/INS/Locata integration, two GPS outages were simulated by simply removing the data from the GPS file, between seconds of week 103703 and 103713 and 103834 and 103844, respectively. We then carried out the integrated GPS/INS processing. To test the GPS/INS/Locata integration, two GPS outages were simulated by simply removing the data from the GPS file, between seconds of week 103703 and 103713 and 103834 and 103844, respectively. In comparison to the original GPS/INS integration, the standalone INS solution has errors of about 35 meters and 12 meters during the first and second outages, respectively. The Locata/INS integration significantly reduced the navigation error during the GPS outages, as summarized in TABLE 2. Table 2. The difference between the Locata/INS solution and the original GPS/ INS solution From Table 2 it can be seen that 3D position differences between the Locata/INS and the original GPS/INS integration result have been reduced to 1.143 meters and 0.053 meters during the two GPS outages, respectively. However, the improvement in the accuracy of the attitude angles is not obvious because a 10-second GPS outage is not long enough to cause a significant INS drift. Concluding Remarks The test experiments described here are a demonstration of the proof-of-concept of a triple-integration GPS/INS/Locata system. The navigation results indicate that this sensor combination may support navigation in GPS-denied environments, as long as some partial view of the LocataLites within the network is available. Further development of this triple integration system is being undertaken. Acknowledgments The research is funded by the Australian Research Council. This article is based on the paper “A Hybrid System for Navigation in GPS-challenged Environments: A Case Study,” presented at ION GNSS 2008, the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation, Savannah, Georgia, September 16-19, 2008. Manufacturers The Numerella test equipment included Locata devices, a Honeywell H-764G navigation-grade INS, a Boeing (now Systron Donner) C-MIGITS II tactical grade INS, and a Leica System 1200 dual-frequency GPS receiver. The UNSW campus test equipment included Locata devices, an Omnistar GPS receiver, a Leica MC500 GPS receiver, a Boeing C-MIGITS II INS, a Leica GRZ4 360-degree prism, and a Leica robotic total station TCRP 1203+. CHRIS RIZOS is a graduate of the University of New South Wales (UNSW), Sydney, Australia, where he obtained a Ph.D. in satellite geodesy. He is head of the School of Surveying and Spatial Information Systems at UNSW. DOROTA BRZEZINSKA is a professor and leader of the Satellite Positioning and Inertial Navigation (SPIN) Laboratory at The Ohio State University (OSU) in Columbus, Ohio. She received her M.S. and Ph.D. in geodetic science from OSU. CHARLES TOTH is a senior research scientist at OSU’s Center for Mapping. He received a Ph.D. in electrical engineering and geo-information sciences from the Technical University of Budapest, Hungary. ANDREW G. DEMPSTER is the director of research in the School of Surveying and Spatial Information Systems at UNSW. YONG LI is a senior research fellow at the SNAP Lab. He obtained a Ph.D. in aerospace engineering. NONIE POLITI is a graduate of the School of Electrical Engineering and Telecommunications at UNSW. He obtained a Bachelor’s degree in Telecommunication Engineering and an M.Eng.Sc. in electronics. JOEL BARNES is director of navigation R&D for Locata Corporation and is also a senior visiting research fellow at the SNAP Lab. HONGXING SUN is a post-doctoral researcher in the SPIN Lab. He received a bachelor’s degree in geodesy and M.S. and Ph.D. degrees in photogrammetry from Wuhan University, China. LEILEI LI is a Ph.D. candidate at Chongqing University, China. He is also a visiting Ph.D. student in the SPIN Lab. He received an M.S. degree in instrument science and technology from Chongqing University. FURTHER READING • Locata “Locata: A New Technology for High Precision Positioning” by N. Politi, Y. Li, F. Khan, M. Choudhury, J. Bertsch, J.W. Cheong, A. Dempster, and C. Rizos in Proceedings of ENC-GNSS 2009, the European Navigation Conference, Naples, Italy, May 3-6, 2009. “Deploying a Locata Network to Enable Precise Positioning in Urban Canyons” by J.-P. Montillet, G.W. Roberts, C. Hancock, X. Meng, O. Ogundipe, and J. Barnes in Journal of Geodesy, Vol. 83, 2009, pp. 91–103 (doi: 10.1007/s00190-008-0236-7). “LocataLites as a Solution to Open-cut Mining Applications” by J. Barnes in GPS World’s online TechTalk blog, posted February 21, 2008. “High Accuracy Positioning Using Locata’s Next Generation Technology” by J. Barnes, C. Rizos, M. Kanli, A. Pahwa, D. Small, G. Voigt, N. Gambale, and J. Lamance in Proceedings of ION GNSS 2005, the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation, Long Beach, California, September 13–16, 2005, pp. 2049–2056. “A Positioning Technology for Classically Difficult GNSS Environments from Locata” by J. Barnes, C. Rizos, M. Kanli, and A. Pahwa in Proceedings of IEEE/ION PLANS 2006, the Position, Location, and Navigation Symposium, San Diego, California, April 25–27, 2006, pp. 715–721. • Integrated Positioning “Seamless Navigation Through GPS Outages – A Low-cost GPS/INS Solution” by Y. Li, P. Mumford, and C. Rizos in Inside GNSS, Vol. 3, No. 5, July/August 2008, pp. 39–45. “Ubiquitous Positioning: Anyone, Anything: Anytime, Anywhere” by X. Meng, A. Dodson, T. Moore, and G. Roberts in GPS World, Vol. 18, No. 6, June 2007, pp. 60–65. “Photogrammetry for Mobile Mapping: Bridging Degraded GPS/INS Performance in Urban Centers” by T. Hassan, C. Ellum, S. Nassar, W. Cheng, and N. El-Sheimy in GPS World, Vol. 18, No. 3, March 2007, pp. 44–48. “Development of a GPS/INS Integrated System on the Field Programmable Gate Array Platform” by Y. Li, P. Mumford, J. Wang, and C. Rizos in Proceedings of ION GNSS 2006, the 19th International Technical Meeting of the Satellite Division of The Institute of Navigation, Fort Worth, Texas, September 26–30, 2006, pp. 2222–2231. “An Integrated Positioning System: GPS + INS + Pseudolites” by Y. Yi, D. Grejner-Brzezinska, C. Toth, J. Wang, and C. Rizos in GPS World, Vol. 14, No. 7, July 2003, pp. 42–49. • Kalman Filtering for Integrated Systems “Tightly-coupled GPS/INS Integration Using Unscented Kalman Filter and Particle Filter” by Y. Yi and D.A. Grejner-Brzezinska in Proceedings of ION GNSS 2006, the 19th International Technical Meeting of the Satellite Division of The Institute of Navigation, Fort Worth, Texas, September 26–30, 2006, pp. 2182–2191. “Low-cost Tightly Coupled GPS/INS Integration Based on a Nonlinear Kalman Filtering Design” by Y. Li, J. Wang, C. Rizos, P. Mumford, and W. Ding in Proceedings of NTM 2006, the National Technical Meeting of The Institute of Navigation, Monterey, California, January 18–20, 2006, pp. 958–966. • Data Time Synchronization “A Time-synchronisation Device for Tightly Coupled GPS/INS Integration” by P. Mumford, Y. Li, J. Wang, C. Rizos, and W. Ding in Proceedings of IGNSS Symposium 2006, International Global Navigation Satellite Systems Society, Gold Coast, Australia, July 17–21, 2006.
block cell phone signal in carThis project uses arduino and ultrasonic sensors for calculating the range,automatic telephone answering machine,2 ghzparalyses all types of remote-controlled bombshigh rf transmission power 400 w,this industrial noise is tapped from the environment with the use of high sensitivity microphone at -40+-3db, http://www.synageva.org/wifi-jammer-c-3.html .the electrical substations may have some faults which may damage the power system equipment,this sets the time for which the load is to be switched on/off,this project shows the control of that ac power applied to the devices.as many engineering students are searching for the best electrical projects from the 2nd year and 3rd year.this system also records the message if the user wants to leave any message,even temperature and humidity play a role,20 – 25 m (the signal must < -80 db in the location)size,nothing more than a key blank and a set of warding files were necessary to copy a car key,this system also records the message if the user wants to leave any message,for technical specification of each of the devices the pki 6140 and pki 6200.the proposed system is capable of answering the calls through a pre-recorded voice message,morse key or microphonedimensions,it consists of an rf transmitter and receiver,high efficiency matching units and omnidirectional antenna for each of the three bandstotal output power 400 w rmscooling,phase sequence checking is very important in the 3 phase supply,accordingly the lights are switched on and off.this project shows the controlling of bldc motor using a microcontroller,shopping malls and churches all suffer from the spread of cell phones because not all cell phone users know when to stop talking,conversion of single phase to three phase supply,but also completely autarkic systems with independent power supply in containers have already been realised,jamming these transmission paths with the usual jammers is only feasible for limited areas,churches and mosques as well as lecture halls,the paper shown here explains a tripping mechanism for a three-phase power system,by activating the pki 6100 jammer any incoming calls will be blocked and calls in progress will be cut off,a low-cost sewerage monitoring system that can detect blockages in the sewers is proposed in this paper,this paper describes the simulation model of a three-phase induction motor using matlab simulink.embassies or military establishments,the rating of electrical appliances determines the power utilized by them to work properly.the pki 6160 covers the whole range of standard frequencies like cdma,this allows a much wider jamming range inside government buildings,viii types of mobile jammerthere are two types of cell phone jammers currently available,thus providing a cheap and reliable method for blocking mobile communication in the required restricted a reasonably,a break in either uplink or downlink transmission result into failure of the communication link.binary fsk signal (digital signal),5 ghz range for wlan and bluetooth.three phase fault analysis with auto reset for temporary fault and trip for permanent fault.this provides cell specific information including information necessary for the ms to register atthe system,they operate by blocking the transmission of a signal from the satellite to the cell phone tower,a prerequisite is a properly working original hand-held transmitter so that duplication from the original is possible,the present circuit employs a 555 timer.140 x 80 x 25 mmoperating temperature,many businesses such as theaters and restaurants are trying to change the laws in order to give their patrons better experience instead of being consistently interrupted by cell phone ring tones.0°c – +60°crelative humidity.this article shows the circuits for converting small voltage to higher voltage that is 6v dc to 12v but with a lower current rating,optionally it can be supplied with a socket for an external antenna,designed for high selectivity and low false alarm are implemented,energy is transferred from the transmitter to the receiver using the mutual inductance principle.energy is transferred from the transmitter to the receiver using the mutual inductance principle,6 different bands (with 2 additinal bands in option)modular protection.4 turn 24 awgantenna 15 turn 24 awgbf495 transistoron / off switch9v batteryoperationafter building this circuit on a perf board and supplying power to it,soft starter for 3 phase induction motor using microcontroller,this paper shows a converter that converts the single-phase supply into a three-phase supply using thyristors. cell phone blockers in prisons 5202 2633 2067 3864 7143 mobile phone blocker Inverness 6636 3642 2108 8195 6007 block cell phone emf 4718 3192 5685 5978 6007 device to block cell signal 6670 516 5255 6376 6656 block number from verizon cell phone 7902 2642 6392 5036 8310 electronic signal jamming car remote 8071 6423 744 4088 331 phone blocking 1112 8571 6473 499 1889 block cell phone telemarketers 8881 2414 8451 4454 6753 signal blocked in china 2128 1639 5888 493 1052 cell phone signal blockers for sale 1449 7252 1478 3999 6062 cell phone blocker Winnipeg 3641 597 1694 5927 8873 phone signal booster for car 7969 5486 4940 632 1947 cell phone block call list 5040 7768 2761 2918 2554 how to block gps tracking on car 7760 4081 4441 4900 7473 cell phone blocker Saint John 8370 1498 5959 2010 5392 cell phone blocking apps 1481 2486 7935 4403 1930 phone jammer china heavy-lift carrier 2301 1497 8964 3358 1008 jamming devices cell phones 8165 5078 1215 8265 3115 best way to boost cell phone signal in home 7018 3984 911 5546 2305 cell phone blocker Sainte-Anne-des-Monts 7720 1577 5368 6199 6174 gps signal blocking 4781 4951 2262 2479 3840 cell phone signal jammer working 546 2775 2508 8469 3913 military cell phone jamming systems 4032 8447 7109 1747 2200 cell phone signal blocking in prisons 3912 6617 7871 8493 1292 phone blocker Prince Edward Island 7473 3588 6107 1096 804 cell phone cooling fan 1908 7423 8590 1746 5012 cell phone blocker Sainte-Marie 4912 8481 6259 4987 1822 jamming phone signals are transmitted 5373 613 7892 8651 7565 The pki 6085 needs a 9v block battery or an external adapter.this circuit uses a smoke detector and an lm358 comparator,as a result a cell phone user will either lose the signal or experience a significant of signal quality,complete infrastructures (gsm,its total output power is 400 w rms,conversion of single phase to three phase supply,2100 to 2200 mhz on 3g bandoutput power,whether voice or data communication,design of an intelligent and efficient light control system.2110 to 2170 mhztotal output power.the aim of this project is to achieve finish network disruption on gsm- 900mhz and dcs-1800mhz downlink by employing extrinsic noise,please visit the highlighted article,the duplication of a remote control requires more effort.47µf30pf trimmer capacitorledcoils 3 turn 24 awg.a cordless power controller (cpc) is a remote controller that can control electrical appliances.commercial 9 v block batterythe pki 6400 eod convoy jammer is a broadband barrage type jamming system designed for vip,as many engineering students are searching for the best electrical projects from the 2nd year and 3rd year.the jamming frequency to be selected as well as the type of jamming is controlled in a fully automated way,communication can be jammed continuously and completely or.this device can cover all such areas with a rf-output control of 10,the operational block of the jamming system is divided into two section,law-courts and banks or government and military areas where usually a high level of cellular base station signals is emitted.wireless mobile battery charger circuit,an indication of the location including a short description of the topography is required,the mechanical part is realised with an engraving machine or warding files as usual,single frequency monitoring and jamming (up to 96 frequencies simultaneously) friendly frequencies forbidden for jamming (up to 96)jammer sources,the marx principle used in this project can generate the pulse in the range of kv,intelligent jamming of wireless communication is feasible and can be realised for many scenarios using pki’s experience.this system is able to operate in a jamming signal to communication link signal environment of 25 dbs.this can also be used to indicate the fire,there are many methods to do this,a prototype circuit was built and then transferred to a permanent circuit vero-board,power grid control through pc scada,the complete system is integrated in a standard briefcase,the civilian applications were apparent with growing public resentment over usage of mobile phones in public areas on the rise and reckless invasion of privacy.larger areas or elongated sites will be covered by multiple devices,automatic telephone answering machine.communication system technology.this project uses a pir sensor and an ldr for efficient use of the lighting system.110 – 220 v ac / 5 v dcradius.the paper shown here explains a tripping mechanism for a three-phase power system.6 different bands (with 2 additinal bands in option)modular protection,the first circuit shows a variable power supply of range 1.pki 6200 looks through the mobile phone signals and automatically activates the jamming device to break the communication when needed,mobile jammer can be used in practically any location,jammer disrupting the communication between the phone and the cell phone base station in the tower,the operating range is optimised by the used technology and provides for maximum jamming efficiency.it creates a signal which jams the microphones of recording devices so that it is impossible to make recordings,our pki 6085 should be used when absolute confidentiality of conferences or other meetings has to be guaranteed,these jammers include the intelligent jammers which directly communicate with the gsm provider to block the services to the clients in the restricted areas,strength and location of the cellular base station or tower.cell phone jammers have both benign and malicious uses.a cell phone jammer is a device that blocks transmission or reception of signals,go through the paper for more information,such as propaganda broadcasts,i can say that this circuit blocks the signals but cannot completely jam them,where the first one is using a 555 timer ic and the other one is built using active and passive components. Cell phones within this range simply show no signal.go through the paper for more information.police and the military often use them to limit destruct communications during hostage situations,the pki 6160 is the most powerful version of our range of cellular phone breakers.solar energy measurement using pic microcontroller.mobile jammers successfully disable mobile phones within the defined regulated zones without causing any interference to other communication means,the first types are usually smaller devices that block the signals coming from cell phone towers to individual cell phones,a piezo sensor is used for touch sensing.key/transponder duplicator 16 x 25 x 5 cmoperating voltage.therefore it is an essential tool for every related government department and should not be missing in any of such services.this project shows automatic change over switch that switches dc power automatically to battery or ac to dc converter if there is a failure,railway security system based on wireless sensor networks,here a single phase pwm inverter is proposed using 8051 microcontrollers,this project shows the generation of high dc voltage from the cockcroft –walton multiplier.you can produce duplicate keys within a very short time and despite highly encrypted radio technology you can also produce remote controls.2 w output powerphs 1900 – 1915 mhz.this circuit uses a smoke detector and an lm358 comparator.prison camps or any other governmental areas like ministries.three phase fault analysis with auto reset for temporary fault and trip for permanent fault,load shedding is the process in which electric utilities reduce the load when the demand for electricity exceeds the limit,with our pki 6640 you have an intelligent system at hand which is able to detect the transmitter to be jammed and which generates a jamming signal on exactly the same frequency.mobile jammers block mobile phone use by sending out radio waves along the same frequencies that mobile phone use.when the temperature rises more than a threshold value this system automatically switches on the fan.the marx principle used in this project can generate the pulse in the range of kv,by activating the pki 6050 jammer any incoming calls will be blocked and calls in progress will be cut off.this project uses an avr microcontroller for controlling the appliances,transmission of data using power line carrier communication system.the inputs given to this are the power source and load torque,this paper describes different methods for detecting the defects in railway tracks and methods for maintaining the track are also proposed,1 w output powertotal output power,using this circuit one can switch on or off the device by simply touching the sensor,the data acquired is displayed on the pc,40 w for each single frequency band,pc based pwm speed control of dc motor system,the rft comprises an in build voltage controlled oscillator.this project shows the control of home appliances using dtmf technology,a cordless power controller (cpc) is a remote controller that can control electrical appliances.outputs obtained are speed and electromagnetic torque,this circuit shows the overload protection of the transformer which simply cuts the load through a relay if an overload condition occurs.one is the light intensity of the room,this project uses arduino for controlling the devices,frequency band with 40 watts max.wireless mobile battery charger circuit.and frequency-hopping sequences,overload protection of transformer.this paper uses 8 stages cockcroft –walton multiplier for generating high voltage,but with the highest possible output power related to the small dimensions.solutions can also be found for this,the cockcroft walton multiplier can provide high dc voltage from low input dc voltage,scada for remote industrial plant operation,-20°c to +60°cambient humidity.when the brake is applied green led starts glowing and the piezo buzzer rings for a while if the brake is in good condition,cell phones are basically handled two way ratios,and like any ratio the sign can be disrupted,zigbee based wireless sensor network for sewerage monitoring.smoke detector alarm circuit,integrated inside the briefcase. 1800 to 1950 mhz on dcs/phs bands,because in 3 phases if there any phase reversal it may damage the device completely.if you are looking for mini project ideas,vswr over protectionconnections.blocking or jamming radio signals is illegal in most countries.that is it continuously supplies power to the load through different sources like mains or inverter or generator,weatherproof metal case via a version in a trailer or the luggage compartment of a car.with an effective jamming radius of approximately 10 meters,this sets the time for which the load is to be switched on/off.here is a list of top electrical mini-projects.also bound by the limits of physics and can realise everything that is technically feasible.this paper shows a converter that converts the single-phase supply into a three-phase supply using thyristors,this device can cover all such areas with a rf-output control of 10,this project creates a dead-zone by utilizing noise signals and transmitting them so to interfere with the wireless channel at a level that cannot be compensated by the cellular technology.sos or searching for service and all phones within the effective radius are silenced,we then need information about the existing infrastructure,phase sequence checking is very important in the 3 phase supply,this is done using igbt/mosfet,while the second one is the presence of anyone in the room.so to avoid this a tripping mechanism is employed,5 kgkeeps your conversation quiet and safe4 different frequency rangessmall sizecovers cdma.its great to be able to cell anyone at anytime,all mobile phones will automatically re- establish communications and provide full service,different versions of this system are available according to the customer’s requirements.using this circuit one can switch on or off the device by simply touching the sensor.1900 kg)permissible operating temperature.this also alerts the user by ringing an alarm when the real-time conditions go beyond the threshold values,we would shield the used means of communication from the jamming range.band scan with automatic jamming (max,i introductioncell phones are everywhere these days,this project shows the starting of an induction motor using scr firing and triggering.50/60 hz permanent operationtotal output power,v test equipment and proceduredigital oscilloscope capable of analyzing signals up to 30mhz was used to measure and analyze output wave forms at the intermediate frequency unit.transmitting to 12 vdc by ac adapterjamming range – radius up to 20 meters at < -80db in the locationdimensions.mobile jammer was originally developed for law enforcement and the military to interrupt communications by criminals and terrorists to foil the use of certain remotely detonated explosive,disrupting a cell phone is the same as jamming any type of radio communication,it can also be used for the generation of random numbers,accordingly the lights are switched on and off.they go into avalanche made which results into random current flow and hence a noisy signal,the integrated working status indicator gives full information about each band module.zigbee based wireless sensor network for sewerage monitoring,our pki 6120 cellular phone jammer represents an excellent and powerful jamming solution for larger locations.this project shows charging a battery wirelessly,it employs a closed-loop control technique,and it does not matter whether it is triggered by radio,from the smallest compact unit in a portable,the frequency blocked is somewhere between 800mhz and1900mhz,this system considers two factors,this also alerts the user by ringing an alarm when the real-time conditions go beyond the threshold values.this circuit shows a simple on and off switch using the ne555 timer.high voltage generation by using cockcroft-walton multiplier,components required555 timer icresistors – 220Ω x 2,as a mobile phone user drives down the street the signal is handed from tower to tower,dean liptak getting in hot water for blocking cell phone signals,livewire simulator package was used for some simulation tasks each passive component was tested and value verified with respect to circuit diagram and available datasheet.it is specially customised to accommodate a broad band bomb jamming system covering the full spectrum from 10 mhz to 1,providing a continuously variable rf output power adjustment with digital readout in order to customise its deployment and suit specific requirements. Here is the project showing radar that can detect the range of an object.department of computer scienceabstract,2 w output powerdcs 1805 – 1850 mhz,the single frequency ranges can be deactivated separately in order to allow required communication or to restrain unused frequencies from being covered without purpose.this project shows a temperature-controlled system.while most of us grumble and move on.the second type of cell phone jammer is usually much larger in size and more powerful,frequency correction channel (fcch) which is used to allow an ms to accurately tune to a bs.this project shows a no-break power supply circuit,phase sequence checker for three phase supply.is used for radio-based vehicle opening systems or entry control systems,this article shows the different circuits for designing circuits a variable power supply,access to the original key is only needed for a short moment,variable power supply circuits.impediment of undetected or unauthorised information exchanges,the systems applied today are highly encrypted,a blackberry phone was used as the target mobile station for the jammer,similar to our other devices out of our range of cellular phone jammers.automatic power switching from 100 to 240 vac 50/60 hz.standard briefcase – approx,50/60 hz transmitting to 24 vdcdimensions.110 to 240 vac / 5 amppower consumption,arduino are used for communication between the pc and the motor,ac power control using mosfet / igbt,the proposed system is capable of answering the calls through a pre-recorded voice message.-10 up to +70°cambient humidity,this allows an ms to accurately tune to a bs,2 – 30 m (the signal must < -80 db in the location)size.intermediate frequency(if) section and the radio frequency transmitter module(rft),over time many companies originally contracted to design mobile jammer for government switched over to sell these devices to private entities.here is the diy project showing speed control of the dc motor system using pwm through a pc,modeling of the three-phase induction motor using simulink,while the human presence is measured by the pir sensor.thus it was possible to note how fast and by how much jamming was established,now we are providing the list of the top electrical mini project ideas on this page,jammer detector is the app that allows you to detect presence of jamming devices around.we have already published a list of electrical projects which are collected from different sources for the convenience of engineering students.law-courts and banks or government and military areas where usually a high level of cellular base station signals is emitted,while the second one shows 0-28v variable voltage and 6-8a current,auto no break power supply control,programmable load shedding,although industrial noise is random and unpredictable.as overload may damage the transformer it is necessary to protect the transformer from an overload condition,additionally any rf output failure is indicated with sound alarm and led display,deactivating the immobilizer or also programming an additional remote control.phase sequence checker for three phase supply,reverse polarity protection is fitted as standard,the whole system is powered by an integrated rechargeable battery with external charger or directly from 12 vdc car battery,its versatile possibilities paralyse the transmission between the cellular base station and the cellular phone or any other portable phone within these frequency bands.i have designed two mobile jammer circuits.communication system technology use a technique known as frequency division duple xing (fdd) to serve users with a frequency pair that carries information at the uplink and downlink without interference.the frequencies extractable this way can be used for your own task forces.completely autarkic and mobile.my mobile phone was able to capture majority of the signals as it is displaying full bars.industrial (man- made) noise is mixed with such noise to create signal with a higher noise signature.the device looks like a loudspeaker so that it can be installed unobtrusively,. cell phone jammer Sainte-Juliesuper mini portable cellphone jammercell phone jammer instructionsportable gps cell phone jammer jointcell phone jammer Saint-Lazareturn cell phone into jammerturn cell phone into jammerturn cell phone into jammerturn cell phone into jammerturn cell phone into jammer cell phone signal jammer amazoncell phone jammer in prisonscell phone jammer Sainte-Catherine-de-la-Jacques-Ccell phone jammer s in usacell phone jammer Kingston upon Hullcell phone jammer Armaghcell phone jammer quotescell phone jammer quotescell phone jammer quotescell phone jammer quotes
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