201203 March/April 2012 Archives - Page 2 of 2 - Inside GNSS - Global Navigation Satellite Systems Engineering, Policy, and Design

201203 March/April 2012

Satellite Development Advances as GPS Survives Budget Cuts, LightSquared

New GPS III Test Chamber (Lockheed Martin photo)

The United States GPS program is without doubt the elder statesman of GNSS, but it has had some close calls recently.

At the 2012 Munich Satellite Navigation Summit in March, a high-level Department of Transportation offical and the head of the Air Force GPS Directorate hailed continuing progress on the Global Positioning System’s third-generation satellite development and next-generation control segment (OCX), while apparently escaping — relatively unscathed — the dual perils of Congressional budget cuts and LightSquared interference.

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By Inside GNSS

Coarse Time Positioning

Q: What is Coarse Time Positioning and how does it work?  

A: Coarse time positioning is used to provide a position fix using inaccurate time information when tracking sufficiently weak GNSS signals such that the navigation message cannot be extracted reliably. This article presents the key aspects of coarse positioning, including some of its challenges. To start, however, we begin by looking at the role of time within a GNSS receiver.

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By Inside GNSS

The GPS Dot and its Discontents

In-home construction of the first civilian-owned civil GPS spoofer.

Over the last few years, several of us in the GNSS community have done our best to convince our colleagues, policymakers, and the general public that unsavory characters with GNSS jammers or spoofers are a genuine threat to GNSS and an orderly society.

"But who would want to use a jammer or spoofer?” people ask.

My response? Hackers, because they can. Thieves planning to snatch expensive cargo. A moonlighting employee in the company car. Worse yet, state actors or terrorists targeting our national infrastructure.

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By Inside GNSS

One-Centimeter Accuracy with PPP

The navigation message has always been considered an inherent and essential feature of a global satellite navigation system. Its primary objective is to provide receivers with information on the errors of satellite clocks and parameters to compute the positions of satellites, as well as other parameters that help generate more accurate measurements.  

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By Inside GNSS

GNSS Jamming in the Name of Privacy

RF interference (RFI) has been and will continue to be a significant worry for GNSS users. 

Because the signals from GNSS satellites are very weak by the time that user equipment receives and processes them, they are especially vulnerable to RFI. Signals that overlap GNSS frequencies are likely to come from transmitters much closer than the satellites and, consequently, can easily overpower GNSS signals and render them unusable. 

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By Inside GNSS