Terrestrial Laser Scanning Benefits Mining

As companies employ total quality management methods to increase their competitive advantage, terrestrial laser scanning for bulk material measurement and accurate volumetric calculations is becoming vital.

In the real world of volume calculations, there are small changes on surface angles due to slumping of material and other factors. Because Laser scanning collects so many points, these measurements are recorded and translated to the final model. In a recent quarry test, manual readings from the stockpile toe and crest took four hours to collect 400 survey points. In comparison, laser scanning captured more than 1.2 million coordinated survey points in one hour. Operator safety was enhanced with Laser scanning because it was not necessary to physically access the stockpile.

In this example, there was a six percent difference between the volumes calculated by standard methods versus laser scanning, with laser scanning reporting the lesser amount. The model generated from standard survey methods was simplistic in comparison to the Laser scanning model. Common practice is to walk the perimeter of stockpiles taking measurements at the toe, and repeating this at the crest. Toe and crest strings are then joined by a straight line. Slight slumps at various areas on the pile were not recorded and along the entire stockpile the maximum slump difference reached as much as 4 feet. Conventional practices overestimated the total stockpile volume by almost 500,000 cubic feet, equating to 26,000 tons of product. The overestimate of material corresponded to a value of $1.5 million.

Volume errors have far reaching implications in the mining industry: They affect contractor payments when reconciled against end-of-month stockpile tonnage; corporate planning and budgets; and shipping and plant schedules. End of month stockpile calculations are among the most critical survey tasks. Accurate volume calculations and material measurement can impact goals, balances, monthly closures, and assigning human and equipment resources. The quality of the information generated by laser scanning is essential to reconcile the volumetric differences and calculation problems that have existed in the mining business in the past.

In another example that crosses mining and transportation applications, Stewart, Weir & Co., a surveying and mapping firm from Edmonton, Alberta, Canada performed a terrestrial laser scanning survey for the Highvale Coal Mine west of Edmonton. The mine supplies coal for two power plants in the area and wanted to expand its mining operations to the south across an existing highway. By agreement with Alberta Transportation, Secondary Highway 627 was to be rerouted through an exhausted area of the mine and the highway and land to the south of the highway was to become part of the active mine area. Stewart, Weir & Co. Ltd. was retained to perform the highway design and project management which involved obtaining proper survey information on a large ditch produced by mining operations which ran across the proposed highway alignment. The ditch was approximately 40 meters deep, 150 meters wide, and 1.3 kilometers in length with cliffs on the south side and severe side slopes of native material on the north side of the gorge. The problem facing the surveyors was how to acquire accurate survey data economically and above all, safely.

A conventional survey of the ditch with a reflectorless total station was considered but, due to the width of the ditch, the setup positions, safety concerns, and the amount of information required, it was deemed uneconomical. The solution was to use an Optech ILRIS-3D laser scanner to scan the entire ditch and generate a series of X,Y,Z, coordinates that can be imported into downstream engineering software for volume calculations and the design phase of the project. The end result is a complete data set that accurately and completely mapped the entire area regardless of the terrain and access limitations. The determination of break lines by field staff during the survey is time consuming and in this particular case, impossible to obtain by manual methods. Due to the large amount information gathered at the site, break lines were not required to be surveyed in the field or generated during the processing stage with the point cloud data.

Laser scanner provides several advantages over conventional surveying methods for mining and transportation applications. Limited time on a site and the elimination of the need to physically access a site drastically increases safety for all concerned. Plus, the vast volumes of data obtained offer far greater accuracy than other methods and jobs can be completed in days rather than weeks.

To learn more about terrestrial laser scanning technologies, how they can benefit your spatial information needs, or just for general information, contact us: On the web, www.spatialresources.com; by email, info@spatialresources.com; or call one of our advisors at 720-934-2482.

Until next time...
Cheers!

Roland Mangold