The Questionable Future of GPS
Technological change can bring dramatic improvements, even in surveying. But a key part of moving ahead is that new technologies should only displace others if they are replacement technologies. Today, a looming communications technology threatens to doom GPS, a crucial positioning (and timing) technology, by displacing it without providing an alternative. That threat comes from one company’s plans to implement what is called long-term evolution (LTE) to support the move in the U.S. by cell phone network providers to the 4G cellular wireless standard.
GPS is an essential tool for most land surveyors and geomatics professionals today, but it may not be so ubiquitous in the future. LightSquared is a beltway corporation (located in the Washington, D.C., metro area) intent on revolutionizing “…the way Americans connect with each other and with the world,” in part by transmitting high-powered wireless broadband signals. In November, the company applied to the FCC for a waiver to effectively repurpose specific bands of the radio spectrum. If approved, up to 40,000 ground transmitters will broadcast in a frequency band adjoining the portion of the spectrum that GPS uses.
LightSquared arrived at this solution after acquiring a satellite communications company with permits to work in this section of the frequency spectrum. Satellite communications and GPS both have signals that are in the neighborhood of the same intensity when received on the ground, and the FCC allocates this public resource in such a way so as to cause minimum interference with other users. But the new application asks for permission to install vast networks of high-powered ground-based transmitters to operate on the same frequency currently assigned predominantly to low-power signals from space.
The potential problem can be explained by this simplified example. Driving down the road listening to an FM station, you may have heard interference from another station or from a citizen’s band (CB) or ham radio transmission. This usually occurs even when the offending transmission is not at your listening frequency when the power of that intruding signal is many times the power of the signal from your favorite station. In the case of the broadband network proposed by LightSquared, simulations done by engineering teams at GPS companies show that signals from the terrestrial transmitters might be as much as one billion times stronger than the GPS signal as received on earth. When this happens, it will jam the GPS signal.
The FCC has had a reputation for being slow to make decisions on applications, taking time to weigh input from all those affected and conducting and reviewing painstaking research. With LightSquared’s application, however, the FCC has uncharacteristically moved with breathtaking speed, granting a conditional waiver this year to allow the company to begin testing and building infrastructure to implement its plan. It’s worth noting that the FCC has a National Broadband Plan (www.broadband.gov/plan) that is aggressively trying to carry out a Congressional mandate to bring broadband services to more than 100 million currently unserved citizens and to improve connectivity and capacity for those who are served.
The reaction from providers and user groups has been strong. Ken Mooyman, president of Hexagon Geosystems, NAFTA said, “Leica Geosystems, as a provider of GPS-based technologies for surveying, mapping, construction and related activities, is very concerned about the potential effects on end user GPS performance should the conditional waiver to LightSquared become permanent. We hope the FCC will consider all impacts before making any final decision. We particularly welcome the FCC inviting potentially affected parties to be fully heard before making a final decision. Some of our products in fact access broadband to be able to work effectively, such as with SmartNet solutions (RTK GPS). However we cannot sacrifice robust GPS operation to get good-quality Internet connections.”
Eduardo Falcon, senior vice president of the Emerging Business Unit at Topcon Positioning Systems, said that compromising the widespread GPS services to benefit the commercial interest of an individual communications company should be exposed to the public as an economic threat. “What would be the reaction of the U.S. government to a foreign threat of interference to our GPS-based services?,” he said. “The LightSquared proposal presents similar risks to consumer and professional use of GPS and, therefore, would have an adverse effect on the economic health of the U.S.”
MAPPS, an association of private-sector geospatial firms, has filed a letter with the FCC expressing concern for the LightSquared application and the potential impact on GPS users. ACSM also filed a letter with the FCC expressing concern about the application as well as an Application for Review of the conditional waiver. And ASPRS, the imaging and geospatial information society, has indicated that it, too, is concerned about the issue.
As industries affected by this potential threat tried to organize, the Association of Equipment Manufacturers (AEM, which has a Geospatial Industry Group) hosted a Washington, D.C., briefing of industry groups and member companies in late February regarding the FCC interim decision, and it continues to provide leadership on the issue.
The issue presents a conundrum. How can one part of the federal government be so willing to easily accept a plan that--theoretically, at least*--causes disruption of a technology that has gained ubiquitous acceptance and use in the United States and globally? The Global Positioning System is a dual-use system that was researched, designed, implemented and operated by the U.S. Department of Defense, with civilian representation through the National Executive Committee for Space-Based Positioning, Navigation and Timing. Although originally only military users were considered, it soon became apparent that GPS had utility in many non-military applications.
Since the system’s launch, the number of producers of GPS hardware, developers of systems that integrate this potent capability for precise positioning (and ultra-precise time), and users (that is, those with GPS receivers) has multiplied by leaps and bounds, giving rise to significant economic contributions. It can be argued that GPS has even increased the quality of life for many, both within and outside of the United States.
At the same time, connectivity to the Internet is being recognized as a basic service that all citizens must have. This connectivity has the potential to be a driver of economic benefits that will rival and possibly overshadow those of GPS. It can also be argued that Internet connectivity stands to potentially increase the quality of life for many people in the U.S. and around the world.
Surveyors, mappers and other geomatics professionals must act now to preserve GPS. While the waiver granted to LightSquared is still conditional, we must communicate our concerns about permitting a broadband technology that jeopardizes GPS operation. It is imperative that the FCC be completely assured that GPS signal reception by current users is not reduced before giving LightSquared final approval. If the research shows any adverse impact, the FCC should ask LightSquared for an alternate technology plan. The national desire to increase broadband accessibility, and LightSquared’s desire to fulfill it, should be possible through other means.
A “Coalition to Save Our GPS” has been formed to safeguard GPS (see www.saveourgps.org). Although associations we belong to and companies we do business with may have joined the coalition and filed letters and papers with the FCC and Congressional representatives, each of us as individuals and the organizations we represent (both private and public) must also lend our voices as part of the groundswell reaction to this unprecedented move by the FCC.
* At press time, no known “live” testing had yet been performed to evaluate the impact of the network on GPS signals.