Official U.S. Government information about the
Global Positioning System (GPS) and related topics
Frequently Asked Questions
Problems
- GPS devices show my home/business in the wrong place or give bad route directions. What should I do?
- I lost my mobile phone/device. Can GPS help me find it?
- How do I check for and report GPS service outages?
Concerns
- 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?
- Is it true the Air Force doesn't want to use GPS in the future because of its vulnerabilities?
- Are GPS jamming devices legal?
- What is the potential for a gap in GPS service?
- Is it true the Census Bureau recorded the GPS coordinates of my home?
- Is 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?
GPS 101
- How does GPS work?
- How accurate is GPS?
- Is military GPS more accurate than civilian GPS?
- How many satellites are in the GPS constellation?
- Who pays for GPS?
- Has the government considered privatizing GPS?
- Where can I download high-resolution images of the GPS satellites?
GPS devices show my home/business in the wrong place. What should I do?
Visit the Address, Route, & Map Problems page for instructions on how to submit corrections to the responsible parties. Go there
Return to top of pageI lost my mobile phone/device. Can GPS help me find it?
We recommend you contact your wireless carrier. They may be able to track down your phone/device using the location technology built into it.
Please be aware that the GPS satellites themselves do not track anything on the ground. They are simply beacons, like lighthouses, broadcasting one-way reference signals. Therefore, the government operators of GPS cannot locate your phone/device.
Where do I check for and report GPS service outages?
The GPS Service Outages & Status Reports page provides points of contact for reporting GPS outages, interference, and other anomalies to the government. 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 GPS unit can lose reception in the presence of devices designed for intentional radio jamming. Solar flares can also disrupt GPS equipment. For this reason, the U.S. government strongly encourages all GPS users to maintain backup/alternative positioning, navigation, and timing capabilities. In addition, the government is currently fielding new GPS signals that are more resistant to interference.
Commercial aircraft 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. Air traffic control would continue to provide surveillance services and ensure aircraft separation.
Is it true the Air Force doesn't want to use GPS in the future because of its vulnerabilities?
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
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
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
Is 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
How does GPS work?
Our educational poster explains the basic concepts behind satellite navigation. View it
In addition, our Video Messages page includes several videos addressing the topic. Go there
How accurate is GPS?
Is military GPS more accurate than civilian GPS?
Answers are on the GPS Accuracy page. Go there
How many satellites are in the GPS constellation?
The Air Force manages the constellation to ensure the availability of at least 24 GPS satellites, 95% of the time. For the past several years, the Air Force has been flying 31 operational GPS satellites, plus 3-5 decommissioned satellites ("residuals") that can be reactivated if needed. Learn more
Who pays for GPS?
Has the government considered privatizing GPS?
Answers are on the Program Funding page. 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
