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Columns and Editorials

LightSquared: Who Pays for GPS Receiver Fixes Yet to be Devised?

With more testing on the horizon and a potentially alarming homeland security report about to be released, LightSquared’s efforts to begin work on its proposed wireless broadband service are stuck in the procedural mud.

The delays, which are never good for a commercial company, are piling up just as the firm’s coffers are thinning and need to be replenished with a new round of fund raising.

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By Dee Ann Divis
September 14, 2011

GNSS Hotspots

One of 12 magnetograms recorded at Greenwich Observatory during the Great Geomagnetic Storm of 1859
1996 soccer game in the Midwest, (Rick Dikeman image)
Nouméa ground station after the flood
A pencil and a coffee cup show the size of NASA’s teeny tiny PhoneSat
Bonus Hotspot: Naro Tartaruga AUV
Pacific lamprey spawning (photo by Jeremy Monroe, Fresh Waters Illustrated)
“Return of the Bucentaurn to the Molo on Ascension Day”, by (Giovanni Antonio Canal) Canaletto
The U.S. Naval Observatory Alternate Master Clock at 2nd Space Operations Squadron, Schriever AFB in Colorado. This photo was taken in January, 2006 during the addition of a leap second. The USNO master clocks control GPS timing. They are accurate to within one second every 20 million years (Satellites are so picky! Humans, on the other hand, just want to know if we’re too late for lunch) USAF photo by A1C Jason Ridder.
Detail of Compass/ BeiDou2 system diagram
Hotspot 6: Beluga A300 600ST

1. HERE, KITTY KITTY
Santa Cruz, California USA
√ First, get the cougar on the treadmill . . . that’s what UC Santa Cruz researchers did to measure baseline behavior and design a tool that tells what puma concolor do every minute. Their super-advanced CARNIVORE collar uses GNSS and a 3-axis accelerometer to create a 24-hour diary of the wild life.

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By Inside GNSS
September 13, 2011

Worst GPS President Ever?

First, let’s review the record of presidential leadership in GPS.

In 1983, following the shooting down of an errant Korean airliner over Soviet airspace, President Ronald Reagan ordered the U.S. Air Force to make GPS available for civilian use so that such navigational errors could be avoided in the future.

George H. W. Bush was commander in chief in 1991 during the first Persian Gulf when GPS helped coalition troops throw the so-called “left hook” by navigating through the desert around entrenched Iraqi troops in Kuwait.

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By Inside GNSS

The Differences in Differencing

Equation 1

Q: How does measurement differencing affect my computed position?

A: The short answer is, “That depends.”

Standalone, or undifferenced, measurements obviously produce the poorest positioning performance. However, how we proceed from this most basic data processing approach may affect the computed solution. In this article, we look at the details of why this occurs.

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By Inside GNSS
July 28, 2011

GNSS Hotspots

One of 12 magnetograms recorded at Greenwich Observatory during the Great Geomagnetic Storm of 1859
1996 soccer game in the Midwest, (Rick Dikeman image)
Nouméa ground station after the flood
A pencil and a coffee cup show the size of NASA’s teeny tiny PhoneSat
Bonus Hotspot: Naro Tartaruga AUV
Pacific lamprey spawning (photo by Jeremy Monroe, Fresh Waters Illustrated)
“Return of the Bucentaurn to the Molo on Ascension Day”, by (Giovanni Antonio Canal) Canaletto
The U.S. Naval Observatory Alternate Master Clock at 2nd Space Operations Squadron, Schriever AFB in Colorado. This photo was taken in January, 2006 during the addition of a leap second. The USNO master clocks control GPS timing. They are accurate to within one second every 20 million years (Satellites are so picky! Humans, on the other hand, just want to know if we’re too late for lunch) USAF photo by A1C Jason Ridder.
Detail of Compass/ BeiDou2 system diagram
Hotspot 6: Beluga A300 600ST

1. AQUARIUS
Buenos Aires, Argentina and Vandenberg AFB, California, USA

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By Inside GNSS
July 26, 2011

The Fire Next Time

What have we learned from the LightSquared fiasco?

Aside from the fact that someone gambling with other people’s money, with friends in high places benefiting from his largesse, can make the law stand on its head and our hair stand on end.

But then, we already knew that.

Just because the forces behind the broadband cellular company, Philip Falcone and Harbinger Investments, made their money by betting against the housing bubble doesn’t take away from the fact that they represent the same crew who helped take down the world economy in 2007.

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By Inside GNSS

GNSS-Based Attitude Determination

FIGURE 1: Heading, bank and elevation angles of an actual platform carrying two perpendicular two meter-long baselines. The attitude solutions are shown for both the derived, or float, measurements (top), as well as the carrier phase-based, or fixed, measurements obtained after having correctly resolved the integer ambiguities (bottom). Precision differs between the methods by two orders of magnitude. Gray dots represent the two-dimensional projections on each of the three coordinate planes.

Working Papers explore the technical and scientific themes that underpin GNSS programs and applications. This regular column is coordinated by Prof. Dr.-Ing. Günter Hein, head of Europe’s Galileo Operations and Evolution.

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By Inside GNSS

What is a virtual reference station and how does it work?

Q: What is a virtual reference station and how does it work?

A: To reach centimeter-level — or even better — accuracy of positioning typically requires use of precise dual-frequency carrier phase observations. Furthermore, these observations are usually processed using a differential GNSS (DGNSS) algorithm, such as real time kinematic (RTK) or post-processing (PP). Regardless of the specific differential algorithm, however, implicit in the process is an assumption that the quality of the reference station data is consistent with the desired level of positioning accuracy.

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By Inside GNSS