A Policy Direction for the Global Positioning System: Balancing National Security and Commercial Interests

• 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

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 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.

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

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.

Preferred Forms of GPS Governance

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.

RB-1501