GPS Source, a manufacturer of indoor GPS receivers, released its GLI-Metro-G system, which provides a variety of GPS signal types and control over effective radiated power (ERP) levels. GLI-Metro-G can receive GPS L1/L2 and Glonass L1/L2 signals, and users can select both GPS and Glonass or each type individually. An antenna must be mounted on the outside of the building to pass the signals through to the receiver. GLI-Metro-G will also accept Galileo signals when that system becomes operative, as well as those from other future GPS-type systems.
Today, most of us would probably rate cellphones, ATMs and the Internet as the three most useful modern gadgets we use regularly. We likely wouldn’t rank GPS up there, and maybe not even in the top 10. Yet without GPS, those three wouldn’t work too well, if at all, and neither would a host of other things that we depend on (reliable electrical power; banking systems; national and worldwide telecommunications, including air traffic control; and car navigation, to name a few). And with NextGen slowly approaching, aviation’s dependence on GPS will grow exponentially.
Testifying before Congress in May, Stanford University professor Brad Parkinson–the chief architect of GPS and the original GPS program manager before his retirement from the USAF–echoed the concern of the Government Accountability Office (GAO) that there will be insufficient backup satellites to fill gaps in the constellation before the DOD’s forecast 2014 launches of its next-generation GPS III units. (see AIN, June, page one.)
One key benefit of the future GPS III satellites that the DOD plans to launch in 2014 is that they will transmit a second civil aviation signal, called L-5, that new receivers will compare with today’s L-1 civil signals to eliminate ionospheric interference, the last major cause of GPS errors.
A study from the U.S. Government Accountability Office (GAO) predicts that GPS service levels could fall well below civil requirements in the next decade. GPS typically has 24 satellites in orbit, although it currently has 31.
While GPS is currently leading the pack in terms of satnav system implementation, at a recent UN International Committee on Global Navigation Satellite Systems conference it was clear that competing systems are getting closer and could overtake it during the next decade. Presentations from Europe, Russia and China described active developments of worldwide satnav constellations, while India and Japan are moving ahead with regional networks.
The DOT Volpe Center’s September 10 report on the vulnerability of GPS to jamming and other interference, in addition to the events of the following day, have greatly heightened national concerns about the security of the satellite system and the degree of dependence that should be placed on it as the backbone of our future ATC system.
DOT Secretary Norman Mineta announced last month an action plan aimed at mitigating the vulnerability of GPS to inadvertent interference and deliberate jamming, both of which were disclosed in a September 10 report by the DOT’s Volpe National Transportation Systems Center in Cambridge, Mass.
Navstar, the official U.S. Air Force program moniker for the constellation of satellites most of us refer to simply as GPS, has undergone a multitude of technical changes and upgrades in the nearly 30 years since a group of military and civil engineers first sat down in the Pentagon to talk about the far-reaching precision navigation concept.
The FAA’s original plan to transition to sole-means GPS is no longer practical and some form of backup will be required for the foreseeable future, according to speakers at a recent Navigation Industry Day. This event was sponsored by the DOT, FAA and Civil Aviation Advanced Systems Development (CAASD), which is a component of the federally-funded MITRE research and development center and a key FAA think-tank resource.
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