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the processing workstation in the engineering office was established via fiber-optic cable. Signals <br />from nine surface stations above the longwall panels were sampled continuously with remote <br />digitizers and transmitted to a data acquisition node on the LAN in the engineering office via three <br />900-MHz, spread-spectrum transceiver pairs. Data from several isolated surface stations were also <br />occasionally merged with data from the main networks in post-collection processing and analysis. <br />A second processing and display workstation node was placed in the shift bosses' meeting room <br />where seismic tomography and longwall shield pressure data were also being archived and <br />analyzed (Westman et al., 2001). <br />Remote digitizer <br /> - V <br /> s~rum <br />Spread R°"'°te digitizer <br />Multichannel GPS Remote digitizer <br />serial port Modem (IRIG) <br />~ <br />_ o <br /> <br />Data acquisition Foreman's room <br /> Data processing <br />Surface <br /> Fiber optic <br /> transceiver <br /> <br />.~, Digitizer <br />Fiber optic Data acquisition <br />transceiver Geophones <br />Underground <br />Figure 4. Willow Creek Mine network. <br />Bowie No. 2 Mine <br />Remote PC-104 data acquisition platforms and a wireless LAN were deployed at [he Bowie No. 2 <br />longwall coat mine in western Colorado. The surface above [his mine possesses many of [he <br />geographical bamers commonly found in westem coal mines-steep, rugged terrain and dense <br />vegetation. It is this sort of situation [hat motivated the development of the distributed network <br />approach to seismic data acquisition. Depth of cover over individual panels varies from 50 m (165 <br />ft) to greater than 500 m (1,600 ft). Three small seismometer arrays were deployed in areas where <br />convenient access through the dense vegetation was possible. Figure 5 shows two arrays deployed <br />