When coal is mined it is generally stored in a temporary stockpile. Depending on demand levels it may be stored in a ROM (run of mine) or dump station prior to being transferred to the wash plant (or coal handling preparation plant) for preparation for leaving site. The wash plant will usually have stockpiles of coal ready to be loaded on trains at any given time. Stockpile surveys are conducted monthly to monitor the amount of coal which has been mined and is available and also to check for discrepancies between truck load reports and train load reports.

Topsoil stockpiles are also monitored. Any topsoil that is excavated can be used for rehabilitation at a later date, so it is usually stored in stockpiles ready for future use. Surveyors will monitor these stockpiles and provide volumes for topsoil that is available.

The method of monitoring these volumes depends on the resources, size and finances available at each mine. At some mines, surveyors will use lasers or RTK GPS and take points while walking over the stockpiles, while at others aerial photogrammetry is used. Stockpile volumes are calculated in a similar fashion to pit volumes (see volume calculations section).

Example #1: Stockpile pickup example


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Example #2: Stockpile surface example


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Example #3: Stockpile surface example


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Example #4: Photo of coal stockpile


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Example #5: Photo of coal stockpiles


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Being such an old profession; with many methods and ways of doing things remaining fundamentally similar, it is always exciting to see technology implementations to improve surveying work in speed and accuracy as well as financially.

An interesting article from www.MiningAustralia.com.au (click here for PDF of article) explains the use of Unmanned Aerial Vehicles (UAV) to survey stockpiles using DSLR cameras by flying pre-determined paths using GPS waypoints and stereophotogrammetry to derive survey points for volume calculations to commence. This method is similar to the aerial photogrammetry mentioned earlier however relieves the requirement for a pilot and is likely to allow for mines to purchase their own UAV equipment which could be run at anytime; potentially leading to long-term financial benefits.

Some of the duties undertaken by surveyors in open-cut operations include:
Machine Control
Road and Ramp Set Out
Volume Calculations
Reconciliation
High Wall Surveying
Blast Control
Stockpile Monitoring
Locate Old Underground Workings