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Precise Geodetic Infrastructure: National Requirements for a Shared Resource
THE GEODETIC INFRASTRUCTURE AND SOCIETY
Implicitly or explicitly, nearly all observations of the Earth system and applications derived from those observations depend on the geodetic infrastructure. This report illustrates that the geodetic infrastructure is critical to the ability to understand and respond to such global issues as climate change and natural hazards, and that its impact also permeates our everyday lives. For example, drivers of cars, airplanes, and boats can now use inexpensive GPS receivers to determine their position to sub-meter precision in real time anywhere on the planet. In the foreseeable future, not only will we be able to know a vehicle’s position to centimeter accuracy in real time, but we also may be able to control that position through autonomous navigation systems. Such systems would make possible many tasks offering enormous economic advantages. In addition, future applications of precise geodesy to soil moisture mapping, precise agriculture, transportation systems, and hazard mitigation would have direct economic benefits.
These current and future applications illustrate that the geodetic infrastructure and its related data sets are public goods, in the same sense that national highway systems or weather-prediction services are public goods. Previous National Research Council reports have made the case that raw environmental data are a public good and, as such, should be supported by taxpayers (NRC, 2001). Based on this premise, government agencies have historically covered the costs of building and operating the ground-based networks, observation satellites, and data systems that collect global environmental observations and make them available to researchers and to the public. The long-term support of geodetic equipment, data collection, and data analysis and distribution systems is, in a very direct way, a governmental responsibility that must be incorporated in the permanent mission statements and budgets of relevant state and federal agencies. In addition, because technological progress often arises from research conducted at universities and agencies that are free of any such long-term responsibility, there is a need to systematically transfer technology and expertise gained from geodesy research developments to operational agencies. These agencies must in turn allocate adequate resources and prepare a workforce to take advantage of the geodetic infrastructure and support advanced applications. This is especially true of anticipated future advances, such as those described in Chapter 4.
Geodetic capabilities have advanced by about one order of magnitude per decade since the first satellite operations. This rate of progress shows that a level of performance that is “pushing the envelope” today stands a good chance of becoming tomorrow’s basic requirement. As discussed in Chapters 2 and 3, many aspects of geodetic techniques, technologies, and data analysis are progressing rapidly today; such trends will likely persist in the foreseeable future. For example, societal applications of geodetic imaging, using active remote sensing tools such as radar and LiDAR with increasing spatial and temporal resolution and improving accuracy, will probably contribute powerfully to this progress.
Recognizing the benefits of the geodetic infrastructure to science and society and considering anticipated future needs and advances, the committee developed both short-term and long-term recommendations, which are discussed in the following sections.
THE NATIONAL AND GLOBAL FUNDAMENTAL STATION NETWORK
Chapter 5 illustrates the critical contribution of VLBI and SLR to the determination of the ITRF. VLBI uniquely defines the orientation of the ITRF in space, while SLR provides the precise tie to the origin of the Earth (the geocenter). Together, these techniques provide the only strong constraint on the ITRF “scale,” but both are susceptible to various error sources that need to be controlled. Maintenance of these techniques, therefore, is essential for maintaining the ITRF in order to meet the ever-increasing accuracy demands of current and future geodetic applications. The most effective use of U.S. investments in this equipment, in the context of the global network, would be to upgrade current VLBI and SLR sites that have been occupied for decades, thereby retaining