Quarry Surveying
Volume calculation and extraction planning. El-Eman Office provides quarry and mining surveying.
Geodetic control and control points at the quarry
Accurate quarry surveying relies on a network of fixed control points set up outside the digging and blasting area, because points near the working face can move or be buried. The points are tied to the project's coordinate system and re-checked before every periodic survey, so each comparison between surveys rests on one stable base.
- Choose points on firm, stable ground with a clear view of the sky so GNSS observations are good.
- Mark each point clearly and document it with a description and photos so it can be found later.
- Keep at least two well-separated points so they can check each other during the work.
How excavation volumes are calculated between two surveys
The basic idea is to build a digital surface model before excavation and another after it, then calculate the volume difference between the two surfaces. This can be done in several ways:
- Cross-section method: cross-sections are drawn at regular spacing, the area of each is calculated, and the volume between consecutive sections is derived.
- Digital terrain model (TIN or grid): volumes are computed directly between the surfaces, which is the most accurate approach for irregular ground.
- Reference surface: volume is calculated above or below a set level, which suits stockpile estimates.
It is important to distinguish between volume in place in the rock and volume after extraction and loosening, because loosened material occupies more space. Keep this in mind when linking surveyed quantities to truck loads and sales.
Common mistakes that affect quantity accuracy
- Relying on an old survey that no longer represents the current shape of the site.
- Changing control points between surveys without transforming the coordinates, which produces false volume differences.
- Covering sharp edges and vertical faces with too few points.
- Ignoring overburden, temporary backfill or stockpiles when calculating actual extraction.
- Not documenting the calculation method, which makes differences hard to explain when different parties review them.
It also helps to decide the survey frequency in advance, monthly or quarterly depending on how active the digging is, so production estimates and payments are based on figures that can be checked.
Frequently asked questions
Is a drone survey alone enough to calculate quarry quantities?
It is very useful for covering large areas quickly, but it needs accurately observed ground control points and a field check of shadowed or dusty areas and vertical faces, where gaps can appear.
How often should a quarry be surveyed?
It depends on the production rate and how closely management needs to follow it. The frequency should be set in advance in the work plan. The busier the operation, the more regular the surveys should be to monitor output and slope stability.
Why does the surveyed quantity differ from the quantity sold?
Because a survey measures volume in place, while materials are sold loosened. There is also waste, spoil and temporary stock. Agreed conversion factors are used to link the two figures.
