Blogs

Wide Awake Bridging the Gap

March 30, 2010By

I gave this talk at the Munich Satellite Navigation Summit, in a concluding session titled “Bridging the Gap: A Journalistic View on Progress and Problems of GNSS.” __________ Before telling you what I came here to say today, I should really attempt to answer the question posed by our moderator:Is the world ready for new GNSS applications and services? If... read more

This article is tagged with and posted in All Blogs, Editor's Wide Awake Blog, GNSS

The Spy Who Loved Me

February 16, 2010By

With apologies to James Bond, Ian Fleming, and, well, just about everybody else. Here is a grab from my mail bag.  The message was subject-lined: GPS Spy Applications. “I recently suspected my wife of cheating, having been involved with gps as a land surveyor since 1995, I used and application called mobile-spy. “In order to install the application onto an... read more

This article is tagged with , and posted in All Blogs, Editor's Wide Awake Blog, GNSS, Personal Tracking

Integer ambiguity validation: Still an open problem?

July 30, 2007By

By Sandra Verhagen High-precision Global Navigation Satellite System (GNSS) positioning results are obtained with carrier phase measurements, once the integer cycle ambiguities have been successfully resolved. The position solution is obtained in four steps: 1. Float solution:least-squares, discarding integer nature. 2. Integer solution: real-valued float ambiguities mapped to integer-valued ambiguities.Examples of integer estimators (Teunissen, 1998a): • Integer Least-Squares: optimal, requires... read more

This article is tagged with , and posted in Algorithms & Methods, Tech Talk

Antenna-induced biases in GNSS receivers May 17, 2007

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

This article is tagged with , and posted in OEM, Tech Talk

GPS Transmitter Frequencies

January 16, 2007By

Why are the two GPS Transmitter frequencies (1575.42 and 1227.6 MHz) coherently selected integer multiples of 10.23 MHz master clock? Question posted on CANSPACE on October 30, 2006, by Sivaraman Ranganathan. The document defining the GPS signal, IS-GPS-200, states that “The carrier frequencies for the L1 and L2 signals shall be coherently derived from a common frequency source within the... read more

This article is tagged with and posted in Tech Talk

Why are GLONASS satellites launched on Christmas Day?

January 16, 2007By

Why are GLONASS satellites launched on Christmas Day? Question posted on CANSPACE on December 10, 2006, by Kerry Matthews The latest triple-satellite GLONASS launch occurred on December 25th at 23:18 Moscow Time. This launch is the sixth GLONASS December launch in a row. In fact, all 9 launches since December 1995 have occurred in the last month of the year... read more

This article is tagged with and posted in Tech Talk