| 摘要 |
A system for analyzing three-dimensional seismic data includes a plurality of digitizer units (7), each with a configuration of geophones (8), a data recording and control center (12), a base GPS receiver with an associated antenna (5) with a substantially unrestricted view of the sky and at the respective digitizer units (7) low-power slave GPS receivers (6) that acquire and track GPS satellite (9) signals using tracking assistance information provided by the base GPS receiver. The slave GPS receivers (6) use the tracking assistance information to acquire and track GPS satellite signals that may be relatively weak at the receivers, due to conditions at the site, such as foliage canopies (11) and so forth. The system processes range information provided by the slave GPS receivers (6) over an extended period of time. In this way, the precise positions of the respective slave GPS receivers (6), and thus, the digitizer units, can be calculated, even if the slave GPS receivers (6) are able to observe and collect data from sets of two or more satellites (9) for only three or four relatively short time intervals at various sky positions during the extended period. The slave GPS receivers (6) then locally produce for the digitizer units (7) timing signals that are based on the GPS codes and synchronized across the system. If a given slave GPS receiver (6) cannot, at a given time, track any GPS satellite signals, a nearby slave GPS receiver (6) supplies the timing information required for the geophone data gathering operations.
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