Research Brief

Figure 1. GPS Total U.S. Sales

SOURCE: U.S. GPS Industry Council, March 1995.

The Global Positioning System (GPS) is a constellation of satellites originally deployed to aid U.S. armed forces in navigation and position location. However, over the past 10 years, GPS has evolved far beyond its military origins. It is now an information resource supporting a wide range of civil, scientific, and commercial functions—from air traffic control to the Internet—with precision location and timing information. The market for civilian applications now exceeds its military counterpart by roughly 3 to 1, a ratio expected to grow to 8 to 1 by the end of the 1990s. The growth in civilian applications has spawned a booming market for GPS products and services. According to the GPS Industry Council, projected sales of commercial GPS equipment in the year 2000 are expected to total about $8.5 billion (see Figure 1).

The evolution of GPS into an information system with a substantial international user community has raised complex policy questions for U.S. decisionmakers on a variety of issues affecting national defense, commerce, and foreign policy. These questions fall into four categories:

  • Dual-use: How can GPS policy balance national security and commercial interests most effectively?
  • Funding: Should the U.S. government continue to fund GPS or seek to collect user fees?
  • Governance: How should GPS and associated augmentations be governed in the future?
  • Foreign policy: How should the United States address foreign concerns about continued access to GPS signals and maintenance of a stable policy environment?

RAND/CTI'S GPS Study: Examining the Major Issues

As part of an effort to address these questions, the White House Office of Science and Technology Policy and the National Science and Technology Council asked RAND's Critical Technologies Institute (CTI) to examine the major policy issues surrounding GPS and recommend solutions for addressing them.

CTI's report concludes that a key underlying issue in GPS-related debates is the lack of a clear policy directive from the U.S. government. To remedy this, the government should articulate a directive to provide a framework for the various stakeholders—military, commercial, and international—in GPS applications. This framework should reassure all users that GPS will continue to operate in a stable, reliable manner and provide civilian signals free of direct charges.

The research consisted of three tasks: (1) reviewing the voluminous literature on GPS; (2) interviewing a wide range of government and industry officials, primarily in Washington, D.C., California, and Colorado (where the GPS master control station is located) as well as in Japan and Europe; and (3) conducting analyses on associated topics, such as patent trends in GPS technologies, the effectiveness of ballistic and cruise missiles using GPS, electromagnetic interference problems, and the legal implications of various GPS applications.

Background: How GPS Works

GPS consists of three segments: a space segment—24 orbiting satellites; a control segment, which includes a control center and access to overseas command stations; and a user segment, consisting of GPS user equipment. GPS was developed by the U.S. Department of Defense at a cost of approximately $10 billion and was deployed over two decades.

GPS satellites transmit two different signals—the Precision or P-code and the Coarse Acquisition or C/A-code. The P-code is designed for authorized users and provides accuracy to within a few meters. To ensure that unauthorized users do not acquire the P-code, the United States has encrypted the P-code signal. The C/A-code is designed for nonmilitary users; thus, it is less accurate and easier to jam than the P-code. However, the C/A-code is easier to acquire than the P-code, so military receivers first track the C/A-code and then transfer to the P-code. The U.S. military can degrade the accuracy of the C/A-code by implementing a technique called selective availability (SA) that controls the level of accuracy available to users who rely on the C/A-code alone. Currently, the C/A-code provides users with positions accurate to about 100 meters, whereas the P-code provides an accuracy of 20 meters or better.

Augmentations to GPS can increase the accuracy available to civilian users. Ground stations compare their known locations with GPS-derived positioning measurements. The results, known as differential corrections, are then transmitted to users so they can apply the corrections to their GPS receivers. Differential corrections can improve the accuracy provided by the civilian GPS signal from approximately 100 meters to 5 to 10 meters or less, which is necessary for civilian applications such as precision approaches into harbors and airports. But ground augmentations can also help circumvent the U.S. military's ability to selectively degrade the civilian signal's accuracy.

Figure 2. Augmentations Can Increase the Accuracy of GPS Signals

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Currently, all accuracy augmentations rely on ground-based networks. Thus, accuracy augmentations are available only over local regions within range of appropriate transmitters. In the future, accuracy augmentations may be broadcast from satellites (see Figure 2), which would allow wide-area augmentations of the GPS signal.

Policy Recommendations

GPS enables unique military, commercial, and civil capabilities. The United States has an important opportunity to shape the direction of GPS applications and mitigate the risks of this new technology.

The recommendations of the RAND/CTI study can be divided into three categories: integrating U.S. economic and national security objectives, governance and funding of GPS and its augmentations, and foreign policy. Because of the dual-use nature of GPS, a policy decision in any one of these realms has repercussions for the others.

Integrating Economic and National Security Objectives

  • The United States should issue a national policy statement on GPS to provide a more stable framework for public- and private-sector decisionmaking. This statement should identify U.S. interests and objectives with respect to GPS, address GPS management and acquisition issues, and provide guidance for the development of GPS augmentations and future international agreements.
  • The United States should initiate discussions with Japan and Europe on regional security and economic issues associated with GPS, potentially leading to international agreements. These agreements should be mutually beneficial to all parties but should not involve the exchange of funds.
  • The Department of Defense (DoD) should reduce its reliance on civilian GPS receivers and the C/A-code for military purposes. It should also develop and introduce into operation GPS equipment capable of rapid, direct P-code acquisition.
  • DoD should ensure that it can acquire GPS signals even in a challenged environment and should develop and field anti-jam receivers and antenna enhancements. DoD should also ensure it has adequate electronic countermeasures to selectively deny GPS signals to an adversary.
  • The United States should not preclude or deter private ground augmentation services except for reasons of national security or public safety. In deciding whether civil GPS accuracy augmentations should be selectively deniable, the primary concern should be to balance national security and public safety, while taking international acceptance into account. Commercial concerns are important, but of lower national priority.

Governance and Funding

  • The United States government should ensure that GPS is funded and maintained in a stable manner, free of direct user charges, to promote the adoption of GPS as a global standard for position location, navigation, and timing.
  • The United States should ensure that the GPS space segment remains subject to its control in order to protect its national security interests.
  • Local-area DGPS networks, most of which are already under the control of the private sector and national governments, are not good candidates for international management because of their limited range, strong national interests in retaining local control, and the lack of a means for enforcing international control even assuming this were desirable.
  • International governance of wide-area augmentations would not harm U.S. security interests and would enhance the international acceptance of GPS. It is likely that international organizations, as well as individual nations, would want independent oversight of augmentations to GPS integrity and availability. This oversight may be accommodated in international or regional agreements.

The table below describes preferred governance regimes for the various segments of GPS and its augmentations.

Preferred Forms of GPS Governance

Regime International Regional National/Bilateral Local/Private
GPS segment
Space/control - - X -
User - - - X
Wide-area GPS augmentations
Integrity X X X -
Availability X X X -
Accuracy - - X -
Local-area GPS augmentations - - X X

Foreign Policy

  • The United States should work to minimize international barriers to commercial GPS-related goods and services, such as proprietary standards and inadequate spectrum allocations.
  • However, the United States should refrain, and encourage others to refrain, from providing wide-area augmentations of GPS accuracy until appropriate mechanisms (e.g., military countermeasures or diplomatic agreements) are identified to deal with potential misuse. Subject to international agreements, the United States should encourage international integrity monitoring of GPS for purposes of public safety.

Failure to reassure foreign governments poses risks for continued U.S. preeminence in GPS goods and services. The international environment for GPS can evolve in various directions, depending on the nature of U.S. policy. If the United States actively promotes GPS as a global standard, then it will need to address the dual-use nature of the technology through international agreements. If the United States does not actively support GPS or becomes an unreliable steward, GPS augmentations will move forward independent of U.S. interests, which in turn will encourage the entry of foreign alternatives to GPS. The United States would still have GPS for its own national security purposes, but would risk losing the economic and diplomatic benefits from past investments in GPS.

This report is part of the RAND Corporation research brief series. RAND research briefs present policy-oriented summaries of individual published, peer-reviewed documents or of a body of published work.

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