Design & Test

Spirent Intros Customizable Software for GPS Test, Simulation

June 1, 2007By

Navigation and positioning test system supplier Spirent Communications this week introduced a software suite for the STR4500 GPS simulator, enabling users to generate their own test cases based on motion data that fits their specific requirements, the company said. read more

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Antenna-Induced Biases in GNSS Receivers

May 17, 2007By

By Inder Jeet Gupta It is well known that the phase center of a GNSS antenna can vary with the satellite direction. This phase center movement leads to aspect dependent carrier phase and code phase biases in the satellite signal. For precise geo-location, one needs to characterize the antenna-induced carrier and code phase biases over the upper hemisphere. In the... read more

Innovation: The International GNSS Service: Any Questions? (PDF)

January 1, 2007By

Innovation: The International GNSS Service: Any Questions? (PDF) By Angelyn W. Moore Published: January 2007 GPS World In this month’s column, Angelyn Moore, the IGS Central Bureau’s deputy director, overviews the organization’s service, history, and future, demonstrating that the IGS is a model of scientific collaboration of which not just the GNSS community but the whole world should be proud.—Richard... read more

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Update: GNSS Accuracy: Lies, Damn Lies, and Statistics

January 1, 2007By

This update to a seminal article first published here in 1998 explains how statistical methods can create many different position accuracy measures. As the driving forces of positioning and navigation change from survey and precision guidance to location-based services, E911, and so on, some accuracy measures have fallen out of common usage, while others have blossomed. The analysis changes further when the constellation expands to ombinations of GPS, SBAS, Galileo, and GLONASS. Software scripts, provided online, help bridge the gap between theory and reality. read more

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Potential Problems for Users of Modernized GPS Signals in Mixed-Mode Operations

June 15, 2006By

PRN 17 is the first in the new generation of GPS satellites with a new feature called flex power. read more

Innovation: GNSS Radio (PDF)

May 1, 2006By

Innovation: GNSS Radio: A System Analysis and Algorithm Development Research Tool for PCs (PDF) By J.K. Ray, S.M. Deshpande, R.A. Nayak, and M.E. Cannon Published: May 2006 GPS World In this month’s column, a team of researchers from India and Canada describe a GNSS radio and how they have used it to develop and test algorithms for processing both legacy... read more

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Innovation: Spacecraft Navigator

April 1, 2006By
Figure 1: GPS signal reception at GEO and HEO orbital altitudes.

Autonomous GPS Positioning at High Earth Orbits
To initially acquire the GPS signals, a receiver also would have to search quickly through the much larger range of possible Doppler shifts and code delays than those experienced by a terrestrial receiver. read more

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Innovation: Satellite Navigation Evolution: The Software GNSS Receiver (PDF)

January 1, 2005By

Innovation: Satellite Navigation Evolution: The Software GNSS Receiver (PDF) By Glenn MacGougan, Peter Ludvig Normark, and Christian Stahlberg Published: January 2005 GPS World In this month’s Innovation, we look at a further evolution of the GNSS receiver which offers the promise of flexibility, adaptability, and cost-effectiveness.—Richard Langley read more