Synergism among Applications

There is a synergism between the use of GPS for atmospheric remote sensing and its use for positioning and navigation in the geosciences. The same instrumentation and techniques used to collect atmospheric and meteorological data by observing atmospheric effects on the GPS signal can also be used to account for these effects when determining an accurate position solution. This synergism can be exploited by co-locating reference stations with weather stations and vice versa whenever possible.

Optimizing Network and Reference Site Positioning Accuracy

Further analysis is required to fully understand the relationship between GPS positioning accuracy, data sampling rates, data latency, and sources of error. Most networks cannot be optimized for all potential applications, which makes the relationship between accuracy, sampling rates, data latency, and sources of error very important Some sources of error, such as multipath and other interactions between antennas and the environment are poorly characterized for many existing network reference sites.

Data Dissemination

Real-time continuous dissemination of data derived from GPS observables is vital for dynamic positioning and navigation and is also useful for other applications, including weather forecasting and real-time earthquake monitoring. For other applications, such as climatology and long term geophysical studies, delayed access to data is acceptable.

Network Coordination

Hundreds, perhaps thousands of GPS reference sites comprising a variety of GPS networks will probably be established worldwide in the next several years. These sites and networks will probably be designed according to a number of different standards and specifications based on the requirements of their primary users. In order to maximize the value of these sites to multiple scientific and nonscientific users, however, some level of standardization and coordination will be necessary. This will require the continued involvement of nongovernmental scientific and technical organizations, intergovernmental organizations, and interagency working groups within the borders of the United States.

Communications between Users and Network Operators

Although some scientific researchers may require autonomous control of a GPS reference station and its ancillary equipment, many users only need to know how to obtain data in a timely manner, and if necessary, how to request a configuration change, such as a higher sampling rate, from the operators of existing GPS networks. However, this will require sufficient knowledge of network operations on the part of users to prevent unreasonable requests from interefering with the primary function of a network or reference station. It also requires adequate dissemination of information on the part of network operators and controlling agencies. The creation of a coordinated “catalog” of GPS networks and their technical characteristics, as well as instructions for accessing related data and information systems, may be a useful means of disseminating information to potential users. Posting this catalog on the Internet along with links to each network's controlling organization could also allow users in the scientific community to send feedback, suggestions, and appropriate requests directly to network operators.

Communications between network users and operators can also be fostered through forums like this workshop and the public meetings of the Civil GPS Service Interface Committee established by the U.S. Department of Transportation. Meetings within the scientific disciplines that use GPS could also be effectively used if network operators were encouraged to attend and participate when subjects related to GPS appear on the agenda.

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