Antenna-Induced Biases in GNSS Receivers

May 17, 2007 - By

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

Survey Perspectives – May 2007

May 17, 2007 - By

Whether you live in London, Lagos, Lisbon, or Los Angeles, when you are looking to buy a survey instrument, most likely you have a preferred instrument distributor in mind. Maybe it´s the local Topcon dealer. Perhaps your Leica dealer has served you well. Or you might prefer the Trimble dealer in your area. All of the manufacturers have distributors signed up around the world. Some operate on a regional basis, serving several countries, while others serve one specific country. I raise this point because of recent, significant changes in the U.S. distribution of survey instruments. read more

This article is tagged with and posted in Opinions, Survey

GPS Insights: Looking Aft, Looking Fore

May 8, 2007 - By

Over-the-air television transmitters are located on large Earthbound transmission towers that typically put out a lot of wattage and hence signal strength over a 50- to 100-mile radius. Sounds a lot like a super-sized pseudolite to me. Now this new idea starts to sound a little more plausible, doesn?t it? read more

This article is tagged with and posted in Defense