Column Archives - Page 18 of 18 - Inside GNSS


August 27, 2010

The Missing ICD

Successful launch of three Compass (Beidou-2) satellites so far this year and reports of another two planned later in 2010 have elevated awareness of China’s accelerating GNSS program.

Added to the two spacecraft placed in orbit in 2007 and 2009, that would bring the modernized Beidou constellation up to seven — halfway to the 13 or 14 satellites planned for the regional system scheduled to be available by 2012.

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By Inside GNSS
August 17, 2010

A Search for Spectrum

FIGURE 1: Example of accuracy close to one centimeter provided by the integer ambiguity resolution on undifferenced phase (IARUP) technique using GPS L1 and L2 signals

In recent years, researchers have explored possible new allocations for Radio Determination Satellite Service (RDSS) and Radio Navigation Satellite Service (RNSS) spectrum from a regulatory point of view. These studies have mainly discussed S-band and C-band in addition to L-band.

The International Telecommunications Union (ITU) Radio Regulations define RNSS as a subset of RDSS. Although the allocations are differentiated — RDSS usually has a paired uplink — both can actually be used for satellite navigation.

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By Inside GNSS

A Fully Digital Model for Kalman Filters

Q: Is it possible to define a fully digital state model for Kalman filtering?

A: The Kalman filter is a mathematical method, purpose of which is to process noisy measurements in order to obtain an estimate of some relevant parameters of a system. It represents a valuable tool in the GNSS area, with some of its main applications related to the computation of the user position/velocity/time (PVT) solution and to the integration of GNSS receivers with an inertial navigation system (INS) or other sensors.

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By Inside GNSS
July 21, 2010

Interesting. Too Interesting?

In the world of GNSS we usually think of more as better. More systems, more satellites, more signals — all contribute to greater availability of robust positioning, navigation, and timing.

Certainly that was the mood at the June meeting of the Asia-Pacific Economic Cooperation — GNSS Implementation Team (APEC-GIT) in Seattle, Washington.

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By Inside GNSS
June 22, 2010

Generating Carrier Phase Measurements

Q: What is the carrier phase measurement? How is it generated in GNSS receivers?

A: Simply put, the carrier phase measurement is a measure of the range between a satellite and receiver expressed in units of cycles of the carrier frequency. This measurement can be made with very high precision (of the order of millimeters), but the whole number of cycles between satellite and receiver is not measurable.

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By Inside GNSS
May 31, 2010

Deselecting Unavailability

Only a decade ago, but a world away: 2000.

The last year of the old century that everyone thought was the first of the new.

When flying was still a delight, rather than a worrisome bother.

When the expected — a global Y2K bug–bitten IT meltdown — didn’t happen, and the much-anticipated but still-unexpected did: the United States turned off GPS selective availability.

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By Inside GNSS
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