Algorithms & Methods

Innovation: Carrier-Phase Ambiguity Resolution

April 3, 2015By
FIGURE 9. Network used for the triple-frequency PPP study.

Handling the Biases for Improved Triple-Frequency PPP Convergence
Precise point positioning (PPP) can be considered a viable tool in the kitbag of GPS positioning techniques. One precision aspect of PPP is its use of carrier-phase measurements rather than just pseudoranges. But there is a catch. Often many epochs of measurements are needed for a position solution to converge to a sufficiently high accuracy. In this month’s column, we look at how using measurements from three satellite frequencies rather than just two can help. read more

Galileo E1, E5a Performance for Multi-Frequency, Multi-Constellation GBAS

April 1, 2015By
Pullen-Galileo-O

Analysis of new Galileo signals at an GBAS compares noise and multipath in their performance to GPS L1 and L5. Even after smoothing, Galileo signals perform somewhat better than GPS and are less sensitive to the smoothing time constant. read more

Innovation: Where Are We?

March 5, 2015By
FIGURE 4. Trajectory solutions.

Positioning in Challenging Environments Using Ultra-Wideband Sensor Networks
The use of large transmission bandwidths offers a number of benefits, including accurate ranging and that application in particular is being actively developed for positioning and navigation in environments that are challenging to GNSS such as indoors and built-up areas. In this month’s column, we take a look at the work being carried out in this area by a team of researchers at The Ohio State University. read more

Innovation: A Bright Idea

November 4, 2014By
FIGURE 5. The light of the fourth lamp in the corridor is blocked by shelves, and the corresponding sine-like light pattern does not appear.

Testing the Feasibility of Positioning Using Ambient Light By Jingbin Liu, Ruizhi Chen, Yuwei Chen, Jian Tang, and Juha Hyyppä AND THEN THERE WAS LIGHT. Well, the whole electromagnetic (EM) spectrum, actually. Visible light occupies only a small portion of the spectrum, which extends from below the extremely low frequency (ELF) 3 to 30 hertz band with equivalent wavelengths of... read more

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Innovation: How Deep Is That White Stuff?

September 1, 2014By
FIGURE 6. Aerial view of the forested site (RN86) around the GPS antenna (marked with a circle).

Using GPS Multipath for Snow-Depth Estimation
In this month’s column, we look at a technique that uses interference fringes generated by signals arriving at an antenna directly from GPS satellites and those reflected by snow surrounding the antenna to measure its depth and how it varies over time. GPS for measuring snow depth; who would have thought? read more

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Canadian Science Minister Announces Grant to Langley’s UNB Lab

August 26, 2014By
Professor Langley (center) discusses the UNB geodesy program with Canadian Science Minister Ed Holder (second from left.)

The Canadian Minister of State for science and technology, Ed Holder, visited the University of New Brunswick on July 28 to announce the awarding by the Natural Sciences and Engineering Council of $2.4 million to 28 UNB researchers. He was joined by Keith Ashfield, member of Parliament for Fredericton, where UNB is based, and Craig Leonard, the New Brunswick Minister... read more

Innovation: Ionospheric Modeling Using GPS

February 1, 2014By
FIGURE 2. The network of the four stations used in the evaluation procedures.

Greater Fidelity Using a 3D Approach
In this month’s column we look at the performance of a 3D approach to modeling the ionosphere, including times when the ionosphere is particularly interesting (read disturbed). read more

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Innovation: Cycle Slips

January 1, 2014By
FIGURE 1. A cycle slip affecting phase measurements but not the pseudoranges.

Detection and Correction Using Inertial Aiding
A team of university researchers has developed a technique combining GPS receivers with an inexpensive inertial measuring unit to detect and repair cycle slips with the potential to operate in real time. read more