Pseudolite Applications in Positioning and Navigation: Terminology and Technical Challenges

Problems with existing GNSS systems can be addressed by the inclusion of additional ranging signals transmitted from ground-based “pseudo-satellites” (pseudolites). Pseudolites are an exciting technology that can be used for a wide range of positioning and navigation applications, either as a substantial augmentation tool of space-borne systems, or as an independent system for indoor positioning applications, or as a component to be integrated with inertial/vision sensors. (more…)

In-Vehicle Speech Recognition for Route Navigation

I cannot exactly remember whether I lost my faith in the navigation systems…in Van Wyck or Brooklyn/Queens Express highway? It was a hot summer day, and my friend just picked me up from the JFK airport; she had to get back to her teaching at City College, so, we were in a hurry. Needless to say, it was her first time at the JFK airport, so, we relied on her GPS navigator to take us to Manhattan. We effortlessly got on the Long Island Expressway, and almost passed the toll booth, but since we did not have enough change, we got booked by a cop. Passing a toll booth to enter Long Island Expressway seemed quite normal for the first time, but when we got back to the same toll booth for the second time, and got fined by the same cop, things became a bit surreal. (more…)

Wide-Area RTK Using Data from Internet NTRIP Streams

At present, data from Global Navigation Satellite Systems (GNSS) such as GPS and GLONASS are being streamed over the Internet from receivers at base stations all over the globe. Anyone can receive many of these streams for free. While the quality and availability of the service at any given time is not always guaranteed, many streams have good data available most of the time. Whether their subscription is free or for a fee, the data streams can help a great diversity of users find their precise position in real time. (more…)

Location Privacy: Who Knows Where You Are?

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. (more…)

Real-time performance of independent GNSS integrity monitoring system

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. (more…)

Alignment of a Portable Navigation System

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. (more…)

Typhoons Watch in Taiwan Region Using Precise Point Positioning Technique

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. (more…)

Triple-Frequency Carrier Phase Linear Combinations for GNSS

The GPS modernization program is now in full swing. The benefits of the program have already been seen with the launch of six Block IIR-M satellites transmitting the L2C signal and there is more to come. The next milestone will be the launch of Block IIR-M (20), also known as SVN49, which will carry with it a demonstration payload of the highly anticipated L5 signal. This addition to the GPS constellation will have a significant impact on the number of linear combinations which can be formed from carrier phase observations. (more…)