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

CONCLUSION (cont)
At the 1300 level, the mine coordinate join near the shaft differed by 6 seconds
(higher) than the gyro bearing. This shows a good comparison between the German
gyro controlled coordinates of the wall stations at that level.
The angular misclose in our traverse at 1300 level compared to the initial gyro showed
only 11 arc seconds and, at the 512 level, the difference between the gyro
orientations was 4 arc seconds. After adjustment of our traverse for the angular
miscloses revealed by the gyro orientations and using the coordinates we transferred
to the surface and into the mine, the new coordinate joins differed from the gyro
bearing as follows:
‐ Surface calibration baseline coordinate grid ±0.0 seconds to gyro (datum line)
‐ Surface raise bore baseline coordinate grid ‐0.2 seconds equals gyro
‐ 512 level (shaft) coordinate grid +1.4 arc seconds equals gyro
‐ 512 level (raise bore) coordinate grid +1.0 arc seconds equals gyro
‐ 1300 level (shaft) coordinate grid ‐0.7arc seconds equals gyro
‐ 1300 level (inbye traverse end) coordinate grid +0.3 arc seconds equals gyro