Surveying at Oyu Tolgoi Copper/Gold Mine - Chris Hutchison - AIMS

CONCLUSION (cont)
• Our GAK1 gyro was calibrated at Newcastle University baseline
just prior to departure for Mongolia.
The comparison between our GAK1 and the datum line of
orientation adopted for the project (baseline joining OT13 and
OT11 surface pillars) was GAK1 plus 31.6 arc seconds equals
datum. This rotation of +31.6 arc seconds was applied to all
other gyro orientations to maintain their relativity to the surface
datum line.
At the surface raise bore baseline, the initial gyro comparison
showed that the coordinate join by the mine coordinates differed
by 36 arc seconds (higher) h than the gyro bearing.
At the 512 level, the mine coordinate join at the shaft differed by
7 minutes 36 seconds (higher) than the gyro bearing and 2
minutes 44 seconds (higher) than the gyro bearing at the raise
bore chamber.