January/February 2010

» Subscribe to the print edition for free.
    Allow 6 to 8 weeks for your subscription to be processed.

More precise weapons with GPS on board require more precise and flexible methods of testing them. Here’s a look inside the development of a highly accurate, real-time, portable, and low-cost alternative to traditional weapons testing systems. It incorporates state-of-the-art acoustic, GNSS, and data processing and analysis technologies and has been undergoing tests at the U.S. Army Yuma Proving Ground since May 2009.

GPS modernization includes the monitoring of civil GPS signals - legacy signals and those that will appear over the next few years. In order to carry out the task, however, GPS operators need a comprehensive set of performance specifications. Three experts involved in that effort describe the process and results so far.

The global economic crisis that appeared in summer of 2008 has adversely affected the economies of most European nations. Nonetheless, some market sectors have not suffered as severely as others and, in some cases — including applications of GNSS technologies — have continued to prosper. This essay by economic analysts in the European Commission’s Galileo Unit describes how Galileo, the European global navigation satellite system now under development, can contribute to Europe’s recovery from this crisis.

In this continuing series, the author describes and demonstrates the differences between position accuracy achieved using satellite-receiver pseudoranges and differential pseudoranges compared to the accuracy of carrier phase–aided positioning.

Correct navigation information is key to flight landing procedures, maritime harbor maneuvers and other safety-critical applications. The existing protection level of SBAS + GPS and the alarm limit computation within the Galileo baseline integrity concept will soon give us two approaches to use. Although they both deliver integrity data, each one uses information from the other in unforeseen ways. The authors examine GPS and Galileo integrity methods and propose an algorithm for a reliable combined integrity approach. They also discuss practical issues of implementation and computation of associated protection levels.

With Loran-C’s demise follows the probable abandonment of enhanced Loran (eLoran) as a multimodal backup to GPS. We have to hope that it won’t take a disaster to correct the gaping security hole in our critical national infrastructure for positioning, navigation, and timing (PNT).

Seattle; Cambridge, Massachusetts; Pennsylvania; Kourou space center; London; Russia and Middle-Earth Orbit