Efficient blasting requires constant vigilance with respect to the actual
layout being used in the field. Objective measurement techniques are
required in laying out a pattern as the 'by eye' or 'thumb suck' methods
cannot guarantee consistent results in layout. Erratic blast results are the
consequence of such an approach. In a case study at Sons of Gwalia
mine, it was demonstrated that incorrect front burdens had a snowballing
effect on otherwise carefully laid out blasts, resulting in both excessive
amounts of boulders caused by preconditioning of bench fronts and tops,
and tight digging. Both problems caused lower excavator productivity
and excessive excavator damage, as well as making it difficult to set out
subsequent blasts correctly. Several field measurement methods are
available to aid in determining correct blast layouts and one is described
in this paper.