Assisted seismic measuring system including GPS receivers

Abstract

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

1 . A seismic measurement system including: a plurality of digitizer units and associated geophones for collecting data relating to seismic activities; a base GPS receiver and an associated antenna with a substantial view of the sky, the base GPS receiver acquiring and tracking GPS satellite signals and producing range information; a plurality of slave GPS receivers, one at the location of each digitizer unit, the slave GPS receivers acquiring and tracking GPS satellite signals and producing range information; and a data recording and control center for collecting the range information over an extended period of time and batch processing the information to calculate the positions of the respective slave GPS receivers and associated digitizer units, and collecting and analyzing the data provided by the respective digitizer units to produce seismic measurements.  
   
   
       2 . The system of  claim 1  wherein the base GPS receiver provides tracking assistance information relating to GPS satellites in view; and the slave GPS receivers utilize the tracking assistance information in acquiring and tracking signals from the GPS satellites.  
   
   
       3 . The system of  claim 2  wherein the slave GPS receivers further produce timing signals to control the timing of data collection by the digitizer units.  
   
   
       4 . The system of  claim 2  wherein the data recording and control center returns the calculated positions to the respective slave GPS receivers, and the respective slave GPS receivers utilize the calculated positions and the tracking assistance information to acquire and track signals from at least one GPS satellite and produce timing signals that are tied to the timing of the codes in the tracked GPS satellite signal.  
   
   
       5 . The system of  claim 3  wherein a digitizer unit that is associated with a slave GPS receiver that is not then tracking a GPS satellite signal uses timing signals provided by a nearby slave GPS receiver that is tracking at least one GPS satellite signal.  
   
   
       6 . The system of  claim 1  wherein the antenna associated with the base GPS receiver is located on a tower.  
   
   
       7 . The system of  claim 1  wherein respective slave GPS receivers have restricted views of the sky.  
   
   
       8 . A seismic measurement system including: a plurality of digitizer units and associated geophones for collecting data relating to seismic activities; one or more base GPS receivers with substantial views of at least portions of the sky, the one or more base GPS receivers providing tracking assistance information relating to GPS satellites in view; a plurality of slave GPS receivers at the remaining locations of the digitizer units, the slave GPS receivers utilizing the tracking assistance information to acquire and track signals from the GPS satellites and produce timing signals that are tied to the timing of the codes in the tracked GPS satellite signals to control the timing of data collection by the digitizer units; and a data recording and control center for collecting and analyzing the data provided by the respective digitizer units.  
   
   
       9 . The system of  claim 8  wherein the base and the slave GPS receivers produce associated range information, and the data recording and control center collects the range information from the slave GPS receivers over an extended period of time and batch processes the information to calculate the positions of the respective slave GPS receivers.  
   
   
       10 . The system of  claim 9  wherein the data recording and control center returns the calculated positions to the respective slave GPS receivers, and the respective slave GPS receivers utilize the calculated positions and the tracking assistance information to acquire and track signals from at least one GPS satellite.  
   
   
       11 . The system of  claim 8  wherein the base GPS receivers provide tracking assistance information associated with the portions of the sky for which the views of the respective base GPS receivers are unimpeded.  
   
   
       12 . The system of  claim 8  wherein the one or more base GPS receivers are located respectively at locations of digitizer units.