Satellite Navigation graphic showing various satellite navigation applications

GPS Modernization

GPS modernization is an ongoing effort to upgrade the Global Positioning System with new, advanced capabilities to meet growing military, civil, and commercial needs. The program is being implemented through a series of satellite acquisitions, including GPS Block IIR-M, GPS Block IIF, GPS Block III, and the Next Generation Operational Control System (OCX).

Learn more about GPS modernization at

The Commerce Department's interests/involvement in GPS modernization include the following:

Selective Availability

The first step in the GPS modernization program occurred in May 2000, when the President directed the Department of Defense to end the use of Selective Availability (SA). SA was an intentional degradation of civilian GPS accuracy implemented on a global basis from the GPS satellites. Prior to its deactivation, civil GPS readings could be off by up to 100 meters. After SA was turned off, civil GPS accuracy instantly improved by an order of magnitude, benefiting civil and commercial users worldwide.

The Commerce Department strongly supported ending the use of SA during the policy reviews leading up to the 2000 decision. A Commerce official spoke at the White House event announcing the decision, and the Secretary of Commerce issued a press statement.

In September 2007, the government announced its decision to procure the future generation of GPS satellites (GPS III) without the SA feature. This made the policy decision of 2000 permanent.

Read more about the deactivation of SA... Read the Commerce Secretary's press statement... View NOAA data comparing GPS before and after SA...

New Civilian Signals

The central focus of the GPS modernization program is the addition of new navigation signals to the GPS constellation. The new signals are phasing in incrementally as new GPS satellites are launched to replace older ones. The government is in the process of fielding three new signals designed for civilian use: L2C, L5, and L1C. The legacy civil signal, called L1 C/A or C/A at L1, will also continue broadcasting, for a total of four civil GPS signals in the future.

Second Civil Signal (L2C)

GPS surveyor L2C is the second civilian GPS signal, designed specifically to meet commercial needs. When combined with L1 C/A in a dual-frequency receiver, L2C enables ionospheric correction, a technique that boosts accuracy. For professional users with existing dual-frequency operations, L2C delivers faster signal acquisition, enhanced reliability, and greater operating range.

L2C broadcasts at a higher effective power level than the original L1 C/A signal, making it easier to receive under trees and even indoors. The stronger signal also supports the further miniaturization of low-power GPS chipsets for mobile applications.

The first GPS IIR-M satellite featuring L2C launched in 2005. Every GPS satellite fielded since then has included an L2C transmitter. As of April 10, 2009, there were seven GPS satellites broadcasting L2C.

The Commerce Department strongly supported the development of L2C. NOAA's National Geodetic Survey participated in the design of the signal to maximize its utility to high-precision applications. The Office of Space Commercialization assessed the expected economic benefits of L2C. When the first L2C signal came online in early 2006, the Deputy Secretary of Commerce held a public media event to celebrate its availability.

Read the Deputy Secretary's remarks on L2C... Read more about the economic benefits of L2C...

Third Civil Signal (L5)

L5 is the third civilian GPS signal, broadcast in a radio band reserved exclusively for aviation safety services. With protected spectrum, higher power, greater bandwidth, and other features, L5 is designed to support safety-of-life transportation and other high-performance applications.

airplane cockpitFuture aircraft will use L5 in combination with L1 C/A (also in a protected band) to improve accuracy via ionospheric correction, and to improve robustness via signal redundancy. L5 use will increase capacity, fuel efficiency, and safety in U.S. airspace, railroads, waterways, and highways.

Beyond transportation, L5 will provide users worldwide with the most advanced civilian GPS signal. When used in combination with L1 C/A and L2C, L5 will provide a highly robust service that may enable sub-meter accuracy without augmentations, and very long range operations with augmentations.

The Commerce Department was one of the earliest proponents of a third civil GPS frequency. The National Telecommunications and Information Administration (NTIA), National Geodetic Survey, and Office of Space Commercialization played key roles in the decision making process that led to the selection of the 1176.45 MHz radio frequency for L5 in 1999. With NTIA participation, the International Telecommunication Union (ITU) allocated that spectrum for satellite navigation services at the World Radio Conference in 2000.

In April 2009, the Air Force announced the successful activation of the experimental L5 transmitter on the GPS IIR-20(M) satellite. This was an important step in securing the 1176.45 MHz frequency for use by GPS under ITU rules.

Read the official media release...

The operational L5 signal will launch with the follow-on series of GPS satellites, Block IIF, beginning in May 2010.

Fourth Civil Signal (L1C)

cell phones L1C is the fourth civilian GPS signal, designed to enable interoperability between GPS and international satellite navigation systems. The United States and Europe originally developed L1C as a common civil signal for GPS and Galileo. It features a Multiplexed Binary Offset Carrier (MBOC) waveform designed to improve mobile reception in cities and other challenging environments. Other satellite navigation providers are adopting L1C as a future standard for international interoperability. Japan's Quasi-Zenith Satellite System (QZSS), the Indian Regional Navigation Satellite System (IRNSS), and China's Compass system all plan to broadcast L1C.

The Commerce Department participated in the U.S. negotiations with Europe that led to the emergence of L1C and the 2004 agreement to jointly adopt it.

The United States will launch its first L1C signal with GPS III, starting in the 2016 time frame. L1C will broadcast at the same frequency as the original L1 C/A signal, which will be retained for backwards compatibility.

Economic Benefit Studies

sample graph The Department of Commerce has conducted several analyses of the economic benefits of GPS modernization. The most recent study was an in-depth assessment of the economic benefits of L2C. The study concluded that L2C is likely to generate more than $5.8 billion in user productivity gains over 30 years. The results of the L2C study were released in 2006, shortly after the first L2C broadcast.

Read more about the economic benefits of L2C...

In 1998, the Department worked with the Institute for Defense Analyses (IDA) to perform a quick assessment on the benefits of modernization to U.S. industry. To support this effort, the Deputy of Secretary of Commerce hosted a roundtable meeting with corporate executives from a variety of industrial sectors. The study report supported efforts to accelerate the schedule for L2C implementation from GPS Block IIF to GPS Block IIR-M.

Read more about the 1998 economic assessment...

In 1999, the Department worked with MITRE Corp. to quantify the non-aviation benefits of a third civilian GPS signal. Results of this effort were not released.

Codeless/Semi-Codeless GPS Transition Plan

Many professional GPS receivers attain very high accuracy today by using "codeless" or "semi-codeless" techniques that exploit the encrypted military GPS signals without actually decoding them. Such techniques will no longer be necessary once the new civil GPS signals are fully operational. The government is encouraging all current users of codeless/semi-codeless GPS technology to re-equip to use the modernized civil signals by 2020.

The Department of Commerce played a key role in the decision processes that led to the 2020 sunset date for codeless/semi-codeless GPS access. The Office of Space Commercialization worked hard to raise awareness of the size and significance of the high-end GPS user community, which was poorly understood within the government. The Office collected industry information to quantify the installed base of codeless/semi-codeless GPS equipment, estimate its economic value, and determine an acceptable time frame for its replacement. The Office also issued a request for public comments to receive broad stakeholder feedback.

Read more about the semi-codeless GPS transition plan...

Validation of New Requirements

The Department of Commerce is involved in interagency efforts to implement additional features on future GPS satellites. Such features include: the Distress Alerting Satellite System (DASS) for search and rescue assistance; and satellite laser retroreflectors (SLR) to improve the accuracy of the GPS reference frame. Any new capability proposed for GPS must be validated through an interagency requirements process co-chaired by the Departments of Defense and Transportation.

DASS logo NOAA is working with the Coast Guard, NASA, and the Air Force to validate the requirement to fly DASS as a secondary payload on the GPS satellites. DASS is the follow-on to the current Search and Rescue Satellite Aided Tracking (SARSAT) System that flies on NOAA's meteorological satellites. SARSAT is being phased out in favor of DASS, which will be based in medium earth orbit to improve coverage and response time. If validated for GPS, DASS will fly as a secondary payload on the second block of GPS III satellites. A DASS proof-of-concept payload funded by NASA is on board several GPS satellites today.

Read more about SARSAT at

Civil Funding Strategy

The U.S. Space-Based Positioning, Navigation, and Timing (PNT) Policy assigns the Secretary of Transportation responsibility to provide resources for the implementation of new, civil-unique capabilities on future GPS satellites. Giving the Transportation Department a financial stake in the GPS modernization program is meant to strengthen civilian participation and relieve the Defense Department from paying for GPS features with no military purpose.

Read more about the national policy at

The Commerce Department, as a member of the National Executive Committee for Space-Based PNT, participates in the discussions on how to implement the policy direction. The Office of Space Commercialization participates in legislative outreach efforts to educate Congress on the new funding lines for civil GPS modernization within the Department of Transportation's budget request.

The President's budget request for Fiscal Year 2011 includes $58.5 million within the FAA for civil-unique GPS capabilities. Congress fully funded this activity at $43.4 million in FY 2010 and $20.7 million in FY 2009.

Track the status of civil GPS funding at