Table 4-2 Temporal Resolution Requirements for Dynamic Applications a

Resolution

Application

<0.1 seconds

Mapping

0.1–1.0 seconds

Ionospheric research

1.0–5.0 seconds

Many applications (most pervasive)

>5.0 seconds

Airborne magnetics and some maritime navigation

a The quantitative requirements listed in this table were determined by the remote sensing working group. They do not represent requirements defined by an internationally recognized standardization committee or government agency.

The working group distinguished between the high temporal sampling rates needed at the platform receiver and the sampling rates of GPS observables at reference stations, which are used to determine differential corrections. It was generally agreed that 5-second sampling of correction observables is adequate because factors that influence most known errors do not change very rapidly and because corrections can be interpolated to higher resolution. However, more analysis is needed to determine the sensitivity of final positioning accuracy to the sampling rate of observables used for augmentation. These analyses are important because high-update-rate, real-time corrections could strain the resources of the existing and planned GPS network infrastructure. For example, the real-time positioning and navigation of mobile platforms operating over a wide area requires a wireless broadcast system to disseminate correction data, unlike the batch processing and file transfer methods used in static applications. Because communications bandwidth is an important consideration for wireless broadcasts, efficient data formats must be considered besides the standard receiver-independent exchange (RINEX) format. Minimizing the latency of broadcast corrections is also of considerable importance to real- and near-real-time applications.

For some applications, global GPS network coverage is always desirable and sometimes essential. However, better coverage in critical areas, such as the oceans, may be more important. Incorporating meteorological instrumentation into network reference stations was also discussed. Although meteorological data are not required for most dynamic applications, the data could be used to improve the accuracy of positioning and navigation.

There was general agreement that a second GPS signal dedicated to civilian use would be beneficial. Aside from spectrum allocation, the choice of a center frequency for this new signal should be determined by assessing the trade-offs between separation from the L1 and L2 signals and bandwidth. The working group did not attempt to specify an optimal frequency but generally agreed that a center frequency above both L1 and L2 (1575.42 Mhz and 1227.60 Mhz, respectively) would be desirable. However, because wide bandwidth is important for high resolution and noise reduction, this should take precedence over placement at a higher frequency.



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