Official U.S. Government information about theFrequently Asked Questions
GPS Basics
- How does GPS work?
- Where can I download high-resolution images of the GPS satellites?
- How accurate is GPS?
- Is military GPS more accurate than civilian GPS?
Outages, Interference, and Other Problems
- My GPS device shows my home/business in the wrong place. How do I fix it?
- Where can I report problems with the GPS service?
- Where can I learn about GPS interference from the LightSquared communications network?
- How vulnerable is GPS to malicious jamming? Could a terrorist with a GPS jammer cause airplanes to crash?
- I read the Air Force doesn't want to use GPS in the future because of its vulnerabilities. Is this true?
- Are GPS jamming devices legal?
- Frequently asked questions about GPS jammers (PDF at FCC.gov)
GPS Policy
- Who pays for GPS?
- Isn't GPS under U.S. military control?
- Has the United States ever turned off GPS for military purposes?
- Will the United States ever reactivate Selective Availability?
- Frequently asked questions about Selective Availability
- Has the U.S. government thought about privatizing GPS?
Other Concerns
- What is the potential for a gap in GPS service?
- Will civilian users experience any significant degradation in GPS accuracy or availability in the future?
- Is it true the Census Bureau recorded the GPS coordinates of my home?
How does GPS work?
The Video Messages page contains several videos explaining the basic concept behind satellite navigation. Go there...
Where can I download high-resolution images of the GPS satellites?
The Image Library contains various high-resolution images that have been released into the public domain. Go there...
How accurate is GPS?
Is military GPS more accurate than civilian GPS?
We moved these answers to the GPS Accuracy page. Go there...
My GPS device shows my home/business in the wrong place. How do I fix it?
We published a feature story on this topic in May 2011. Go there...
Where can I report problems with the GPS service?
The GPS User Support page provides links to the appropriate points of contact in the government for reporting GPS outages, interference, and other anomalies. Go there...
Where can I learn about GPS interference from the LightSquared communications network?
We have a page dedicated to this issue. Go there...
How vulnerable is GPS to malicious jamming? Could a terrorist with a GPS jammer cause airplanes to crash?
Like all radio-based services, GPS is subject to interference from both natural and human-made sources. A civilian GPS unit can lose reception in the presence of a device designed for intentional radio jamming. This can also occur during a solar flare. For this reason, the U.S. government strongly encourages all GPS users to maintain backup capabilities for positioning, navigation, and timing. In addition, the government is currently fielding new GPS signals that are more resistant to jamming.
Commercial airliners that use GPS are required to maintain alternative means of navigation. If intentional jamming were directed against aircraft, the pilots would revert to other sensors and ground-based navigation aids.
I read the Air Force doesn't want to use GPS in the future because of its vulnerabilities. Is this true?
The Air Force is fully committed to continuing its operation and use of GPS in the future. The ongoing GPS modernization program will enhance the jam resistance of the military GPS service, making it more robust. At the same time, the Department of Defense is making prudent investments in alternative positioning, navigation, and timing (PNT) technologies to supplement GPS in times when satellite services are unavailable. This will ensure that future troops have continuous, uninterrupted access to PNT under the most challenging conditions.
Are GPS jamming devices legal?
No. We published a feature story on this topic in March 2011. Go there...
Who pays for GPS?
The answer is on Program Funding page. Go there...
Isn't GPS under U.S. military control?
Though acquired and operated by the Department of Defense, GPS is a multi-use system owned by the United States Government and paid for by the U.S. taxpayer. The outstanding performance of GPS over decades has earned the confidence of millions of civil and military users worldwide. The management structure and modernization efforts directed by U.S. policy continue this support for multi-user applications. Any misperceptions will be overcome as they have in the past, by a demonstrated record of service and performance to all users. Learn more...
Has the United States ever turned off GPS for military purposes?
No. Since it was declared operational in 1995, the Global Positioning System has never been deactivated, despite U.S. involvement in wars, anti-terrorism, and other military activities.
Millions of users around the world have been monitoring and recording real-time GPS performance on a continuous basis since its inception. If the civilian GPS service had ever been interrupted by its operators, the evidence would be obvious and widespread. No such evidence exists.
Will the United States ever reactivate Selective Availability?
We moved this answer to its own page. Go there...
Has the U.S. Government thought about privatizing GPS?
We moved this answer to the Program Funding page. Go there...
What is the potential for a gap in GPS service?
The Air Force is confident GPS will continue to meet existing service commitments. Several years ago, the Air Force recognized the potential for an availability gap and took action to institutionalize procedures and processes to mitigate the potential gap or minimize any impact. Air Force Space Command developed key processes within the operational community as well as the acquisition community to extend the life of on-orbit assets and to ensure capability is delivered in a timely manner. Users can employ GPS with confidence today and continue to do so in the future. As identified by the General Accounting Office (GAO) in testimony to Congress, "There have been times before where people have worried about gaps and the Air Force has managed them quite successfully." Learn more...
Will civilian users experience any significant degradation in GPS accuracy or availability in the future?
The Air Force currently foresees no loss of service in the future, near or far. The Air Force has high confidence it will continue to sustain at least the 24 satellites required to maintain the current GPS performance standards. As of December 2010, there were 30 operational satellites orbiting the earth actively broadcasting positioning, navigation, and timing messages to users, 24/7, 365 days a year, around the globe. In addition, the Air Force currently maintains five older satellites on orbit in residual status that can be brought back to operational status if required.
The Air Force is also actively modernizing the constellation, which should enhance the performance and capabilities of the system. The Air Force launched eight GPS Block IIR-M satellites during 2005-2009 and launched the first of 12 GPS Block IIF satellites in May 2010. The next generation of satellites, GPS III, is currently in development and on schedule for a first launch in 2014.
Is it true the Census Bureau recorded the GPS coordinates of my home?
The Census Bureau has published a page addressing their use of GPS. Go there...
