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Columns and Editorials

December 6, 2018

What Is Snapshot Positioning and What Advantages Does It Offer?

Snapshot positioning is a technique for determining the position of a Global Navigation Satellite System (GNSS) receiver using only a very brief interval of the received satellite signal, where the sampling time can be more than 100 milliseconds (ms) or even down to as little as 2 ms. In comparison, a conventional GNSS receiver may require anywhere between a few and tens of seconds of signal tracking before it is able to compute its first position.

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By Mark Petovello

Innovative Test System for GNSS Signal Performance Analysis in Real Environments Part 2

This article — Part 1 was published in the September/October 2018 issue ­— presents the authors’ experience in setting up an airborne pseudolite (UAVlite) with the needed ground-based infrastructure to perform code and phase ranging performance analysis. UAVlites transmit GNSS-like signals free from any local transmitter multipath (in contrast to ground-based transmitters) and can in principle be localized in real-time through a synchronized network of ground stations which may also broadcast the UAVlite positions in real-time.

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By Günter W. Hein
December 4, 2018

GPS Investigations in Japan, and Privacy Concerns

The legal and privacy issues surrounding GPS investigations have come to the forefront around the globe in recent years. Recent court rulings in both Japan and the United States provide insights into the future. Here we summarize and examine a decision by the Japanese Supreme Court and relevant lower court’s decisions, as well compare the Japan decision and the mosaic theory from an earlier U.S. court decision.

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By Ingo Baumann
December 3, 2018

Chris Hegarty – Never A Dull Moment

As anyone who’s been there knows, Boston is one of the best places in America for home-grown Italian cooking. And the city is also home to one of the world’s greatest St. Patrick’s Day parades. Another slightly lesser known but no less impressive product of the Boston melting pot is top-flight GNSS man Christopher Hegarty.

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By Peter Gutierrez
September 25, 2018

Innovative Test System for GNSS Signal Performance Analysis in Real Environments | Part 1

This article presents the authors’ experience in setting up an airborne pseudolite (UAVlite) with the needed ground-based infrastructure to perform code and phase ranging performance analysis. UAVlites transmit GNSS-like signals free from any local transmitter multipath (in contrast to ground-based transmitters) and can in principle be localized in real-time through a synchronized network of ground stations which may also broadcast the UAVlite positions in real-time.

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By Günter W. Hein

GNSS Spoofing and Aviation: An Evolving Relationship

One of the great engineering successes of the International Civil Aviation Organization (ICAO) and its expert panels is the standardization of globally harmonized Communication, Navigation and Surveillance (CNS) systems. These standards, sometimes supported by more detailed industry standards, provide safe and interoperable services between aircraft and the ground and space systems supporting them.

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By Gerhard (Gary) Berz
September 24, 2018

Change Is Coming: 
The Space Force and SMC 2.0

While threats to American defense satellites were climbing sharply, the costs and schedules of U.S. military space programs were on the same unsustainable trajectory — prompting lawmakers last year to begin trying to reorganize Air Force’s military space programs by creating a Space Corps. A move that, so far, has failed.

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By Dee Ann Divis

Are Reflected Signals Always Undesirable?

Rightfully, the GNSS community almost universally considers reflected signals to be problematic (the field GNSS reflectometry being an obvious exception). Reflected or non-line-of-sight (NLOS) signals combine with line-of-sight (LOS) signals to produce multipath effects, or if the LOS signal is absent NLOS signals can produce large ranging biases. Both phenomena increase measurement error and decrease positioning accuracy, especially in areas with lots of reflecting surfaces such as deep urban canyons.

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By Mark Petovello
August 29, 2018

Ligado Fight Comes Down to Choice of Interference Standard

There was a flurry of filings July 9 just as the window closed for public comment on Ligado Networks’ proposal to repurpose satellite frequencies for a terrestrial network — a plan with the potential to interfere with GPS receivers.

The comments emerged as speculation swirled around a July 3 bid by EchoStar for Ligado spectrum supplier INMARSAT. The bid was rejected and, as of press time, EchoStar will have to wait six months before trying again.

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By Dee Ann Divis