International Network of Global Fiducial Stations Science and Implementation Issues (1991) / Chapter Skim
Currently Skimming:
1. Overview
1. Overview
Pages 1-21
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 1... ...
Such an international global network of fiducial stations is the theme of this report. To consider issues raised by the transition to such a network, the Panel on a Global Network of Fiducial Sites was formed by the Committee on Geodesy, National Research Council.
|
From page 2... ...
of very-high-performance stations, operating with a high degree of reliability, many (but not necessarily all) of which would be collocated with other global geodetic and geophysical instruments, thereby providing a common reference frame; fiducial sites, which are defined as stations where geodetic and, if feasible, geophysical measurements are made, continuously or periodically, meeting standards and specifications established for highly precise data.
|
From page 3... ...
This choice of technology influences in turn the nature of the global network. A viable strategy for implementing and operating the network is to integrate existing global networks into a common reference frame and to establish a GPS core network of about 30 or more sites, which permits the definition and realization of the global reference frame and supports the precise determination of orbits and Earth orientation parameters.
|
From page 4... ...
geodetic objectives that call for a global deployment of fiducial sites. These objectives are discussed in detail in Chapter 2.
|
From page 5... ...
. In 1988 the Task Group on Earth Sciences of the Space Science Board National Research Council, produced a seminal report entitled Mission to Planet Earth.
|
From page 6... ...
The associated report, Towards an Integrated System for Measuring Long Term Charges in Global Sea Level (Joint Oceanographic Institutions, 1990) , specifically treats the need for continued development of geodetic techniques on both global and local scales.
|
From page 7... ...
Mission support is therefore a clear motivation for the deployment and operation of global fiducial networks. Finally, a powerful motivation for a global network derives from the support it can afford the geodetic community at large by providing important data products such as precise orbits, a global realization of a terrestrial reference frame, and regional fiducial points to which local and regional networks can easily be tied.
|
From page 8... ...
. From the point of view of a global network of fiducial sites, it is clear that GPS will play a major role in achieving global geodetic coverage.
|
From page 9... ...
Fundamental: The global network will be a primary network to which existing regional networks, or future densification networks, will be linked. An ever-growing proportion of the Earth sciences community is taking a global view of the planet.
|
From page 10... ...
Some networks have evolved from early experiments into an operational mode, while others have been able to build on existing technology into an almost immediately operational system. Current space geodetic techniques can conveniently be classified into optical and radio systems.
|
From page 11... ...
Direct comparisons of coordinates of 16 fiducial sites common to both SLR and VLBI networks have shown agreement at the 2-cm level (e.g., Ray et al., 1991~. The remaining 2 cm could be due to remaining systematic errors in either or both techniques (e.g., water vapor effects for VLBI, orbit errors for SLR, and local survey errors for all space-geodetic techniques)
|
From page 12... ...
The Panel carefully considered the various issues raised by choosing GPS as the prime candidate technology for the global network. Some of these such as reliable, accurate, and timely orbit determination, definition of a terrestrial reference frame; and monitoring of Earth orientation and rotation parameters will be addressed by selecting well-conceived deployment strategies and creating the infrastructure necessary to facilitate global data flow, timely processing, and elective dissemination of data products.
|
From page 13... ...
afion 1: The Panel recommends (IJ incorporating part or all of the existing global GPS networks into a core network of about 30 or more locations as thefirst priority in the deployment of a global network of fiducial sites, primarily to support the reliable determination of precise GPS orbits; (29 maintaining a sufficient level of collocation of different systems, particularly SLR, KLBI, and GPS, to permit realization at the required accuracy of a common reference frame; 639 maintaining a transportable capabilityfor VLBI and SLR systems for occasional verification and validation of long baselines; and (4) planning for long-term reoccupation of sites after transition to a new technique, system, or monument.
|
From page 14... ...
Earth orientation information to be contributed to IERS; and (4) ties to the terrestrial reference frame through collocation at a sufficient number of sites with multiple techniques, specifically fixed and mobile VLBI and SLR equipment, DORIS, and PRARE.
|
From page 15... ...
This recommendation recognizes that existing or planned global networks, including VLBI and QUASAR, SLR, LLR, DORIS, GPS/GLONASS, and PRARE have the potential to satisfy many of the scientific requirements of a global network of fiducial sites. The recommendation also entails strong support for the continued operation of enough sites for each technique, distributed globally and collocated with other techniques, at enough locations to permit the realization, at a sufficient level of accuracy, of a common reference system.
|
From page 16... ...
One of the earliest priorities is to produce and disseminate standard geodetic data products, by operating coordinated data centers to ensure a smoothflow of datafrom the network operators to the user community, and to establish analysis centers to develop and test techniques and results that support part-per-billion three-dimensional geodesy. The creation and operation of these centers should begin concomitantly with the initiation of the GPS core network.
|
From page 17... ...
In the future, global networks will be large, integration of multiple techniques will be required, and demands for rapid data access and rapid data processing and analysis techniques will increase. It is therefore essential that additional global campaigns, such as the proposed IGS Epoch'92 campaign, be executed to prepare for the deployment of a global network of fiducial sites.
|
From page 18... ...
Such a coordination, if effective, could have a major positive impact on the Mission to Planet Earth and may in fact be the best way that the ground segment of this mission can be developed to its full scientific potential. Precise space-geodetic control is of course an essential ingredient of FLINN and is the basis for the long-term goal the Panel set for the global network of fiducial sites.
|
From page 19... ...
Possible Network Configuration After examining many existing global geodetic and geophysical networks (see Chapter 3) , the Panel undertook to map a network configuration with two purposes: (1)
|
From page 21... ...
This is also true of geodesy, and, as the technology becomes available over the next few years, it will become desirable and in some cases imperative to add sea bottom fiducial sites to the global network.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.