ZEB1, which is claimed to be the world’s first truly mobile, hand held, rapid laser mapping system, has been put through a rigorous testing process at one of the world’s deepest gold mines. The lower levels of Anglogold Ashanti’s Mponeng mine are over 2 km below sea level. The ZEB1 was demonstrated in an up-dip stope panel and the resulting 3D model was proven to conform to existing plans of the mine workings. “Before commissioning any new equipment we always undertake rigorous testing as the environment in which we operate is so extreme; with virgin rock temperatures around 60^oC and working temperatures between 30^o and 35^o,” commented Michael Harcombe, Senior Mine Surveyor at the mine. “At these ambient levels, sensitive equipment, such as laser scanners, often just do not work!

“The results of the ZEB1 test were much better than we could possibly have expected,” he continued. “The model generated from the ZEB1 scanning was placed in the mine’s plans for a comparison with the current excavation and found to conform to the outline of the workings. We were hoping to compare the results with our existing laser scanning set up however the test area was simply too small for traditional laser scanners another significant advantage for the ZEB1.”

Mponeng is located between the towns of Carletonville and Fochville on the border between Gauteng and the North West Province, southwest of Johannesburg. The operation extracts the Ventersdorp Contact Reef (VCR) at depths between 2,400 m and 3,900 m by sequential-grid mining producing more than 500,000 oz/y of gold.

Developed by CSIRO and commercialised by UK-based 3D Laser Mapping, ZEB1 uses robotic technology called Simultaneous Localisation and Mapping (SLAM). The system includes a lightweight laser scanner mounted on a simple spring mechanism, which continuously scans as the operator walks through the environment. As the scanner loosely oscillates about a spring it produces a rotation that converts 2D laser measurements into 3D fields of view. Its ability to self-localise makes ZEB1 ideally suited for use underground and in other covered environments where traditional solutions that use GPS don’t function well.

Anglogold Ashanti already operates a traditional terrestrial laser scanner at Mponeng. The RIEGL VZ-400, purchased from 3D Laser Mapping, is used to monitor workings for signs of rock deformation; a common phenomenon at such depths. It also uses the VZ-400 to determine off-line and grade mining, cutting the need for later redevelopment and therefore reworking of areas already mined.