Uncategorized Archives - Page 77 of 81 - Inside GNSS - Global Navigation Satellite Systems Engineering, Policy, and Design


Remote Sensing with Reflected Signals

Generally, a multipath signal in positioning is often considered an undesirable phenomenon that needs to be suppressed. A reflected GNSS signal is one kind of multipath, also known as a scattered signal. Usually, the reflected signal is regarded as an error source that deteriorates the positioning accuracy. But, in fact, these scattered signals can be used in many remote sensing applications.

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Signal Authentication

Brad Parkinson, first director of the GPS Joint Program Office, once remarked that the NAVSTAR Global Positioning System represents, next to the Internet, perhaps the most successful civilian adoption of military-developed, dual-use technology.

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July 27, 2009

GNSS Hotspots | July 2009

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

China Lake, California
√ The U.S. Air Force successfully dropped a live 500-pound GPS-guided missile on target from an MQ-9 Reaper unmanned aerial vehicle at the Naval Air Warfare Center in California on May 13. It’s bound to happen: GPS-assisted UAVs and GPS-aided robots with GPS-guided bombs will carry on our wars without us.

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By Alan Cameron

GPS EASY Suite II: easy13 – RAIM

The usual formulation of position determination involves four unknowns: three physical dimensions (X,Y,Z) and the satellite-receiver time offset. In cases where we can observe five or more pseudoranges, one might well ask if the redundant pseudoranges could be used to check the consistency among the observations —the fundamental principle behind receiver autonomous integrity monitoring (RAIM).

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By Alan Cameron
July 26, 2009

Satellite Numbers Game

The recent GAO report and Government Oversight subcommittee hearing on GPS sustainability generated more heat than light, with some major news media outlets leaving the impression that the sky (or at least GPS satellites) would soon be falling.

Perhaps the only silver lining in the ensuing Chicken Little phenomenon was the crude measure it provided of just how familiar (but not necessarily knowledgeable) private citizens have become with GPS.

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July 4, 2009

Architecture for a Future C-Band/L-band GNSS Mission, Part 2

The downloadable PDF (above) contains bonus material not available in the print edition.

This column continues an exploration of possible use of the C-band radio frequency for GNSS navigation. Part 2 focuses on C-band signal design in the context of non-interference with other services in nearby RF bands, as well as user equipment design and performance.

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What is GNSS repeater-based positioning and how is it different from using pseudolites?

Figure 1: Indoor positioning configuration with switching repeater with multiple re-radiation antennas.

Q: What is GNSS repeater-based positioning and how is it different from using pseudolites?

A: A GNSS repeater is just like a cellular phone repeater that is used to boost the cell phone reception by using a reception antenna, a signal amplifier and an internal rebroadcast antenna. In contrast to cellular broadcast stations, GNSS repeaters are much smaller and often installed inside buildings with an external reception antenna collecting the satellite signals.

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Making Sense of GPS Inter-Signal Corrections

Figure 1

The downloadable PDF (above) contains bonus material not available in the print edition. Appendices and other information on this subject is available at the bottom of the page.

The current version of the master GPS Interface Specification document (IS-GPS-200 Rev D March 2006) contains a new dual-frequency ionosphere correction algorithm that is to be used with the modernized GPS space vehicles (SVs) and their next-generation modernized GPS signals.

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May 15, 2009

16th International Flight Inspection Symposium

IFIS 2010 will be held in Beijing from June 21-25.

The theme is “Improving Flight Inspection for NextGen Technology.” Flight inspection is presented with a host of opportunities and challenges as Satellite-based Navigation and Performance Based Navigation open the way to even more advanced methods of airspace navigation.

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By Inside GNSS
May 5, 2009

European Navigation Conference – ENC-GNSS 2009

The European Navigation Conference 2009 is now underway at Parthenope University in Naples, Italy.

In the opening session on Monday, May 4, the chief engineer for the GPS Wing told the audience that the new L5 demonstration signal transmitted by GPS IIR-20(M) had been experiencing problems and apparently interfering with L1 and L2 legacy signals. Lt. Col. David Goldstein said the Air Force will not launch any more satellites until the cause has been discovered and fixed. 

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By Inside GNSS
April 28, 2009

About BeiDou

China intends to finish their Beidou Navigation Satellite System (BDS, formerly known in English as "Compass") by 2020. When complete, the constellation will will consist of 35
satellites: 5 geostationary orbit (GEO) satellites, 27 in Medium Earth Orbit (MEO) and 3 in Inclined
Geosynchronous Orbit (IGSO).

BDS began providing services to civilian users in China and surrounding areas in the Asia-Pacific in December 2012. 

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By Inside GNSS
April 27, 2009

TRANSNAV Symposium 2009

The 8th navigational symposium on marine navigation and safety of sea transportation will be held at Gdynia Maritime University in June.

Scientists and navigation professionals from a number of countries will share their knowledge, experience and research results in all aspects of navigation, safety of navigation, and sea transportation.

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By Inside GNSS
April 15, 2009

Ka and Broadband Communications, Navigation and Earth Observation Conference

The 15th Ka and Broadband Communications, Navigation and Earth Observation Conference will be held in September at the "T" Hotel in Cagliaria, the capital of Sardinia.

The Italian Space Agency (ASI) conference originally covered satellite communications at 20-30 GHz and higher frequencies. In recent years, it has been expanded to include satellite
broadband communications at all frequencies and satellite-aided navigation.

The event includes the 7th Broadsky Workshop, which will focus on the escalating problems of space debris.

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By Inside GNSS