GPS interference caused by a planned broadband wireless network could cost at least $70 billion and an additional 30 million tons of CO2 over the next 10 years through the loss of efficiency and safety benefits, estimates the FAA.

But LightSquared, which plans to deploy the nationwide network of terrestrial transmitters, says the FAA’s assessment is based on plans that are no longer on the table and does not reflect the latest proposal to use a frequency spectrum that is farthest from GPS.

The FAA report was completed at the request of the government’s National Executive Committee for Space-Based Positioning, Navigation and Timing (PNT), which asked several agencies to assess the impact of GPS receiver interference measured during testing conducted jointly by LightSquared and the GPS community.

That testing, mandated by the U.S. Federal Communications Commission as a condition for approval of LightSquared’s plans, showed significant interference with most GPS receivers from transmission at the higher of the company’s two blocks of spectrum, the one closest to GPS.

As a result, LightSquared at the end of June proposed beginning service with only the lower block of frequencies, which are the farthest from GPS, at lower-than-approved power and to hold off on using the upper band while working to mitigate interference. “LightSquared’s initial operations at the lower 10MHz channel even at ‘reduced’ power levels would impact aviation use of high-precision GPS receivers,” says the executive summary of the FAA report, released by the Save Our GPS coalition.

High-precision receivers are generally regarded as those used for surveying and other purposes, rather than for aircraft navigation, but the executive summary does not explain what the FAA means by “aviation use” of such devices.

According to the report, the FAA “conservatively estimates” that GPS currently provides $200 million a year in efficiency benefits, and that GPS-based safety enhancements “are expected to prevent the loss of approximately 800 lives over the next 10 years” as a result of approach-and-landing accidents, controlled flight into terrain and runway incursions.

The FAA’s impact assessment “does not distinguish between operation in the spectrum farthest from GPS and the spectrum closest to it." Therefore, it doesn’t accurately reflect LightSquared’s most recent proposal, which is focused solely on using the spectrum farthest away from GPS, says Jeff Carlisle, executive VP of regulatory affairs for LightSquared.

The FAA and other agency impact assessments will be forwarded to the National Telecommunications and Information Administration, which will submit the findings to the FCC, says Anthony Russo, director of the national coordination office for PNT. The FCC has called for public comment rule on whether LightSquared can proceed with its revised deployment plan.