The development of Unmanned Aerial Vehicles (UAV) began soon after the first manned flight. The evolution of unmanned systems has lead to a shift from manned to unmanned Intelligence, Surveillance, and Reconnaissance missions which has in-turn lead to an increase in the number of Unmanned Vehicles (UV) operating in a theater. The development of UV technologies has removed the pilot and crew from the vehicle to safe locations. As a result the scale of these vehicles may be reduced considerably, and this reduction in scale allows for increased operation of UVs in Global Positioning System (GPS) degraded environments. With the loss of GPS signal the vehicles are forced to rely on Inertial Navigation Systems (INS) which, when reduced to an appropriate size for these applications, are inherently inaccurate. Read the rest of this entry »

The Air Force Institute of Technology and the Air Force Research Laboratory are cooperating to build non-traditional navigation systems for small autonomous flying vehicles. By definition, these small flying vehicles are able to operate in more cluttered and possibly enclosed environments that are inaccessible to larger aircraft which will expand the intelligence gathering capability required for smaller targets of interest. Unfortunately, the limited size and cluttered operating environment of these vehicles presents a great number of challenges which much be addressed. One of these issues is the development of a navigation system with acceptable accuracy. In previous work, AFIT has developed a tightly-integrated vision/INS navigation system, which can operate in real-time on a PC-chassis. In this paper, a technique is presented to expand the algorithms for to allow implementation on an embedded microprocessor, suitable for use on the class of small UAVs.
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This blog gives a brief description of a new Kalman filter mechanization—the sigmaRho filter—useful for operational implementation in applications where stability and throughput requirements stress traditional implementations. The new mechanization has the benefits of square root filters in both promoting stability and reducing dynamic range of propagated terms. State standard deviations and correlation coefficients are propagated rather than covariance square root elements and these physically meaningful statistics are used to adapt the filtering to further ensure reliable performance. All propagated variables can be scaled to predictable ranges so that a fixed point implementation can be developed. A sample problem from communications signal processing that includes nonlinear state dynamics, extreme time-variation, and extreme range of system eigenvalues shows that the sigmaRho implementation is successfully applied at sample rates approaching 100 MHz to decode binary digital data from a 1.5GHz carrier. Read the rest of this entry »

Introduction

Inertial sensors can be used to provide navigation information for short Global Positioning System (GPS) signals outages. However, very low cost Micro Electro Mechanical Systems (MEMS) inertial sensors, which are desirable for economical reasons, exhibit high biases, scale factor variations, axis non-orthogonalities, drifts and noise characteristics. Any errors mentioned here will directly affect the position, velocity and attitude accuracies as a function of time and therefore, it is important to properly remove these errors before the start of navigation. This article presents a comparison of different methods that can be used for estimation and removal of these errors. A new calibration method is also introduced that does not require proper alignment of the system with the local gravity vector. Read the rest of this entry »

The transmission of GNSS data for RTK surveying was not a goal when the first networks of permanent reference stations for GNSS were built-up. This was also the case for the Swedish national network called SWEPOS, where the first stations were built in the beginning of the 1990’s (Norin et al., 2008). Today (March 2009), SWEPOS has a network RTK service with approximately 1200 registered users that uses mobile telephones to acquire GNSS data for the RTK rovers in the standardized Radio Technical Commission for Maritime Services (RTCM) format. Read the rest of this entry »

Driver Assistance Systems (DAS) play an important role in the navigation of modern vehicles. Such systems are required to assist drivers and for guidance and control of autonomous vehicles on roads and city streets. Today, drivers are already helped by automatic systems among which are the GPS/digital maps navigation systems. However, although a GPS-navigation system can be updated in view of the modifications of the roads, it does not include exhaustive information about the traffic signalisation. The main reason is that traffic signalisation may change without notice. Figure 1 shows some examples of traffic signs. Read the rest of this entry »

GPS-based navigation is quick, drift free, and readily available most of the time. However, as GPS requires direct line of sight signals from at least four GPS satellites, navigation can be frequently interrupted in land based applications. For such situations when the GPS signals are not available, relative navigation can be performed using autonomous sensors. Read the rest of this entry »

The Objective

Typhoons are the most serious weather systems that threaten Taiwan. On average, about four to five typhoons in the western North Pacific affect the island every year, bringing destructive winds and a large amount of rainfall. The economic loss every year due to typhoons could be up to $20 billion. Many meteorological sensors are available for studying the patterns and characteristics of a typhoon. Recently, many studies have used GPS as an alternative meteorological sensor due to the devastating impact of the global climate change. The distributed GPS stations around the earth can serve as a near real-time meteorological sensor network that can be used to detect the potential threats. Read the rest of this entry »

The performance requirements expected from the Global Navigation Satellite Systems (GNSS) are very high. One of the most important demands is effective integrity monitoring. The definition I use here is that integrity is the measure of trust to the computed results, described by the probability that the position error caused by malfunctioning of one of the GNSS components is smaller than expected. Read the rest of this entry »

Engineering advances, like precise and accurate personal positioning systems, are helping to enable a wide range of commercially and socially beneficial information services. In this context, location privacy (the right of individuals to control information about their personal location) can seem a peripheral or puzzling issue for many engineers. As one engineering colleague put it to me: “If you have nothing to hide, why should you be concerned about location privacy?” However, location privacy is increasingly becoming a vital function of any location-based service, and a function that presents spatial information engineers with interesting new challenges. Read the rest of this entry »