Raise boring excavates a circular shaft or hole between two levels without blasting: a machine on the upper level drills a small pilot hole down to a target, then pulls a large reaming head back up to open it to full diameter. The entire result hinges on the accuracy of the pilot hole — and that is a survey-critical task.
Pilot-hole accuracy faces two deviation modes. Corkscrew (spiralling) deviation leaves undulations in the final bored wall that eat into conveyance clearances, while directional deviation is driven by rock structure. Survey House provides the alignment control — accurate collar set-out, verticality reference and, with gyro support, directional feedback during piloting — so deviation is caught and corrected before the far more expensive reaming pass begins.
Accurate alignment ensures the raise connects exactly where intended, keeps conveyance clearances within tolerance, and protects the large capital committed to the reaming operation.
The critical measurement is not the collar setup but the relationship between the two levels. Both positions may be individually correct within their own survey networks and still be wrong relative to each other.
This is why the between-level check is the work that matters. It verifies the two levels against a common reference rather than accepting each level’s own control at face value.
Survey confirms alignment at setup and target position on the level below. Deviation during drilling is a function of the drilling operation and ground conditions.
