July/August 2007

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With the launch of its first middle-earth-orbiting (MEO) Compass satellite, China has put forth its GNSS entry. The key to using and understanding the performance of the Compass M-1 navigation signals is revealed by its spread spectrum code. This article by a team of Stanford University researchers presents the spread spectrum codes being broadcast by this satellite.

On April 14 China launched its first medium-Earth-orbit (MEO) satellite code-named Compass-M1, the first in a planned constellation with global coverage based on the same principles as GPS and Galileo. In order to investigate the space vehicle’s characteristics and data structure, researchers modified a GPS/Galileo hardware receiver so as to track the Compass MEO satellite. This article tells how they did it and presents the first results of their efforts.

The new leader of the U.S. Air Force organization in charge of overseeing the modernized design and acquisition of GPS spacecraft, ground control facilities, and military user equipment outlines his agenda and priorities.

With Russia’s GLONASS undergoing a rapid rebuilding and modernization process, GNSS receiver manufacturers and users have found more reason to consider exploiting the larger number of satellite signals available in a mixed constellation. South Carolina’s Geodetic Survey (SCGS) has put the state on the map as the first to implement a “virtual” reference station network that provides precise real-time differential corrections to both GPS and GLONASS signals. The chief of SCGS and the VRS project manager describe how their agency did it and who’s benefiting from the new statewide service.

I opened the PDF with this month’s cover design from our art director, Tim Jordan, about five minutes after I picked up the morning newspaper. In the paper, a front-page article described our local school district’s plans for starting what would eventually become a 12-year immersion program in Mandarin (putonghua or guoyu). To my way of thinking, the news about the school program was just one more confirmation of our decision not merely to highlight two articles on China’s Compass program on our cover, but to add it to the galaxy of GNSS systems on Inside GNSS’s masthead.

“GNSS Solutions” is a regular column featuring questions and answers about technical aspects of GNSS.

Concerns about the authenticity and security of GNSS signals are usually associated with military applications. On the one hand, military GNSS users need to detect and avoid spoofing — the generation of false ranging signals by an adversary to mislead a foe — while on the other preventing the exploitation of one’s own GNSS broadcasts by an enemy. This two-part column explores the realm of cryptographic tools that can be used to ensure that only authorized users have access to GNSS services and that the positioning information they use — and report — is the real thing.