The Global Positioning System: Assessing National Policies
Dec 1, 1995
Balancing National Security and Commercial Interests
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:
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.
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.
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.
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.
The table below describes preferred governance regimes for the various segments of GPS and its augmentations.
|Wide-area GPS augmentations|
|Local-area GPS augmentations||-||-||X||X|
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.
This document and trademark(s) contained herein are protected by law. This representation of RAND intellectual property is provided for noncommercial use only. Unauthorized posting of this publication online is prohibited; linking directly to this product page is encouraged. Permission is required from RAND to reproduce, or reuse in another form, any of its research documents for commercial purposes. For information on reprint and reuse permissions, please visit www.rand.org/pubs/permissions.
The RAND Corporation is a nonprofit institution that helps improve policy and decisionmaking through research and analysis. RAND's publications do not necessarily reflect the opinions of its research clients and sponsors.