Every time I arrive on-site to gather the day’s information I am continually amazed at the amount of ground that the excavators and the work crew have covered since I was last there. It is always more than I expect. However, it is not so much the amount of work that gets done which is amazing, it is the speed, agility and control that the machine operators display as they are tearing apart the ground which is truly remarkable. Without any hesitations, the massive shovel drops into a pit, in an almost circular trajectory. As it reaches maximum depth, the shovel has already started scooping and pulling back a fine layer of clay that is only a centimeter or two below its last pass. On the way up, the shovel scrapes a tuft of overhanging dirt on one of the banks with great agility. Within seconds the shovel has dumped its load and is on the way back into the hole for a few more modifications.

So how do the workers maintain this incredible accuracy? Experience is necessary, but a great deal of the accuracy is achieved through the use of lasers. A stationary laser unit is set up on a fixed point, usually on the top of a bank, and emits a 360-degree flat plane laser beam. Two receptors, (seen in the above combined photograph), which are actually reflectors, are used in conjunction with the laser unit. One receptor is used for manual measurements and is positioned on a surveying staff, and the other receptor is positioned at an exact height above the excavator’s shovel.

When the laser reflects off one of these receptors, it emits a signalling frequency indicating that the receptor is level with the transmitter. From here, either the exact depth below this level can be measured with the staff, or the sound will signal to the machine operator that the desired depth has been reached.

The laser sending unit emits a flat plane
laser beam 360 degrees around itself.

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