GBM Guidance System
Line and Grade Accuracy for the GBM System
The GBM Guidance System provides line and grade accuracy for the GBM system to within a ¼-in. (6 mm) at 400-ft. (122 m). During operation, an LED target is placed in the lead pilot tube's steering head. The theodolite's cross hairs are aligned to the drive's line and grade and the camera relays this data to the computer controlled digital monitor, mounted to the GBM jacking frame. The operator assesses the target's position from the monitor and makes line and grade adjustments as necessary. The Guidance System assembly consists of a theodolite with remote focus, illuminated LED target, camera, computer controlled digital monitor, lateral slide and elevator column assemblies, counterweight, alignment holder, bore sight laser and protective cases.