Opinions

ACSM/GITA Conference Coverage

May 4, 2010By

The annual ACSM (American Congress on Surveying and Mapping) isn’t what it used to be. Attendance was way down and the number of exhibitors is way down. The technical content, however, was still pretty good. In fact, I've included links to several videos I recorded at the ACSM/GITA conference. 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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SBAS Crashing

April 22, 2010By

It’s been a tough couple of weeks for SBAS (Satellite-Based Augmentation System), namely the USA’s WAAS program and India’s GAGAN program. WAAS and GAGAN have taken big hits recently that threaten the integrity of the programs. Both events were totally unexpected and are causing disruptions of GPS correction services. read more

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Solar Activity and RF ID Technology

April 7, 2010By

It’s time to touch on the solar activity subject again, as there was an event earlier this week and rumors began to fly. The mainstream press jumped on a story back in January when the first solar flare of Solar Cycle 24 occurred. read more

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Out in Front: What’s in a Number?

April 1, 2010By

Computers killed a trusty companion of my teenage years. That is, after those proto-computers known as pocket calculators knocked him out and left him unconscious on the cooling floor. But I come to praise my slide rule, not to bury him. With computers, it’s just numbers in, numbers out. Maybe that high-tech approach led both the GPS Wing and the Government Accountability Office into trouble with constellation gaps. 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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LSAW Conference RTK Network Discussion Roundtable

March 18, 2010By

A couple of weeks ago, I participated in a roundtable discussion at the Land Surveyors Association of Washington (LSAW) annual conference on the subject of RTK networks (RTN). I always enjoy listening to heavy RTK users on their thoughts, their procedures, and how they arrived at them. We danced around a number of subjects with one being the “RTN’s biggest flaw.” My first thought was the communications link, but... read more

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