Expert Advice & Leadership Talks

Expert Advice: Block IIR Lifetimes and GPS Sustainment

November 1, 2010By

In 2009, a Government Accountability Office (GAO) report claimed that the GPS constellation was extremely vulnerable to failure, and a recent September 2010 GAO follow-up continues to make that assertion. In this article, we present the technical data to contradict some of the GAO report conclusions. read more

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Expert Advice: An EPIC Start for Coordination

October 1, 2010By

The new European Positioning, Navigation, and Timing (PNT) Industry Council (EPIC) will be a forum for organizations with an interest in all PNT systems including Global Navigation Satellite Systems (GNSS). EPIC shall serve as an information and distribution portal between all stakeholders in the PNT community. Its mandate includes all GNSS constellations and related augmentation systems worldwide, both operational and in development/modernization. read more

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Expert Advice: Location Changes Everything Mobile

September 1, 2010By

As today’s handsets and consumer devices become more sophisticated, manufacturers continue to incorporate more and more functionality into a small and sleek form factor. Today’s range of smartphones incorporate voice and data transceivers, GPS, Bluetooth, Wi-Fi, cameras, music, touchscreen interfaces, compasses, motion sensors, cameras, storage cards, and many other technologies. Free turn-by-turn navigation services, such as offered on Google Android phones and iPhones, have created a compelling reason for many of us to own a GPS-equipped smartphone. read more

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Expert Advice: Remembering. And Resolving

August 1, 2010By

Few outside the position, navigation, and timing (PNT) community will also recall that the day before the 9/11 attacks, the U.S. government released a landmark document that described the vulnerabilities of services provided by GPS to disruption, whether by attack or inadvertent interference. The Department of Transportation Volpe Center’s GPS vulnerability assessment recommended that services utilizing GPS-provided PNT seek alternative sources of these services. What decisions and actions have the findings and recommendations of this report promoted? The answer is most disturbing. read more

Expert Advice: Moore’s Law and GNSS

July 1, 2010By

I started my relationship with GNSS and Moore’s Law in 1985, writing software for GPS tracking loops on the Advanced Range Instrumentation Aircraft program at the Applied Physics Laboratory of Johns Hopkins University for the U.S. Air Force. The project’s purpose was to navigate a large jet to accurately fly a pattern to drop buoys into the ocean. That receiver had seven circuit boards (six trackers and one navigator) mounted on a VME backplane in a 19-inch rack mount in the back of a C-130, and was about the size and weight of suitcase. read more

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Expert Advice: Quasi-Coherent Delay Lock Loop Tracking and Generalized Binary Coded Symbols in Multipath

May 1, 2010By

The original GPS signals, and indeed most GPS signals including L5, utilize conventional pseudonoise (PN) signal code division multiple access (CDMA), some with both in-phase and quadrature-phase modulation. In the late 1990s, I generalized Manchester PN symbol-spreading by defining split-spectrum binary square wave symbol-spreading, in a series of limited-distribution papers for the Air Force GPS Independent Review Team (IRT). These split-spectrum signals have been developed and analyzed much more fully by many others, and they are now termed binary offset carrier (BOC) modulation. The BOC codes can provide a noise-error advantage by placing more of their spectral energy at an offset frequency, thereby increasing the Gabor bandwidth. They can also provide spectral separation from other GNSS signals in the same frequency band, for example, L1. read more

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Expert Advice: Jamming: A Clear and Present Danger

April 1, 2010By

A packed audience attended the National Physical Laboratory in the United Kingdom for a February 23 meeting titled, “GPS Jamming and Interference: A Clear and Present Danger,” organized by the Digital Systems Knowledge Transfer Network. In his keynote address, David Last described a dark, silent and dangerous world without GPS. His final insight was this: “Navigation is no longer about how to measure where you are accurately. That’s easy. Now it’s how to do so reliably, safely, robustly.” read more

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Expert Advice: Are We There Yet?

March 1, 2010By

At the start of a new decade, let’s examine the state of the GNSS consumer market and technology. In the December 2009 issue of GPS World, I described the developments that put GPS in cell phones over the last decade. That technology revolution has brought GPS a very long way. Having come this far, we can ask that most famous of all navigation questions: Are we there yet? read more