TL;DR
This volumetric surveys FAQ answers what Australian mine managers, quarry operators and civil engineers ask most often before booking a volume measurement. In short: a properly controlled volumetric survey measures stockpiles, pits and earthworks to 1-3% volume accuracy, captures a full run-of-mine pad in a single drone flight, and reports cut-and-fill quantities in your site grid or MGA2020 with heights on AHD. Costs run from roughly $1,500 for a single stockpile to $15,000+ for a multi-area mine reconciliation.
Key takeaways
- A controlled volumetric survey delivers 1-3% volume accuracy on well-defined stockpiles — accurate enough for month-end inventory reconciliation and financial reporting under most Australian mining and accounting requirements.
- Volume is always the difference between two surfaces; the result is only as good as the base surface (the ground beneath the stockpile or the design surface for earthworks), so a known base is critical.
- Drone photogrammetry suits open, accessible stockpiles and ROM pads; terrestrial laser scanning suits indoor sheds, bunded material and steep, shadowed faces a camera cannot resolve.
- Deliverables are georeferenced to GDA2020 / MGA2020 or your established mine grid, with heights reduced to AHD, and include the volume figure, the method, and the surfaces used to derive it.
- Bulk density (tonnage factor) is what converts cubic metres to tonnes — get the density wrong and a perfect volume still produces a wrong tonnage; ISS reports volume and lets your metallurgist apply the agreed factor.
What exactly does a volumetric survey measure?
A volumetric survey measures the space occupied by a body of material — a coal stockpile, an iron-ore ROM pad, a waste dump, a quarry product bay, a bulk-earthworks cut. It does this by capturing the three-dimensional shape of the material's surface and comparing it to a base surface beneath. The volume is the calculated space between the two.
That second surface is the part most people overlook. If you are measuring a stockpile sitting on a concrete pad surveyed when the pad was empty, your volume is reliable. If the stockpile sits on bare ground that has never been surveyed and the base is assumed flat, the figure can be out by far more than the survey's own accuracy. The measurement of the top surface might be millimetre-perfect; the assumption underneath is where the error lives.
Key point A volumetric survey is a difference between two surfaces, not a measurement of one. Always ask which base surface was used — a surveyed pad, a previous survey, or an assumed plane. The answer determines how much you can trust the number.
How accurate is a volumetric survey?
For a well-defined stockpile on a known base, a controlled survey reaches 1-3% volume accuracy. That figure is more than adequate for inventory reconciliation, royalty reporting and reconciling claimed against surveyed quantities. Accuracy depends on three things: control, surface definition, and the base surface.
| Factor | Good case | Poor case |
|---|---|---|
| Survey control | Surveyed GCPs or RTK, checked | Onboard GPS only, unchecked |
| Material surface | Coarse, dry, well-lit, accessible | Fine, wet, shadowed, steep faces |
| Base surface | Surveyed empty pad | Assumed flat plane |
| Typical volume accuracy | 1-3% | 5-15%+ |
Fine, dusty product such as crushed fines or fertiliser is harder for photogrammetry to resolve than coarse run-of-mine rock, and steep faces in deep shadow create gaps. Where those conditions dominate — a covered storage shed, a bunded chemical stockpile, material against a wall — terrestrial laser scanning is the better tool because it measures geometry directly and does not depend on light or texture.
Drone, laser scanner or total station — which method?
The right method is the one that fits the site, not the one a provider happens to own. The three approaches each have a clear niche.
| Method | Best for | Typical strengths |
|---|---|---|
| Drone photogrammetry | Open ROM pads, large stockyards, pits, earthworks | Fast over large areas, removes people from unstable faces |
| Terrestrial laser scanning | Indoor sheds, bunded material, steep/shadowed faces | Direct geometry, works in low light, very dense data |
| Total station / GNSS | Small, accessible piles, quick spot checks | Low mobilisation, simple base surface capture |
A drone flying a Pilbara iron-ore ROM pad or a Bowen Basin coal yard covers the whole area in a single flight and keeps surveyors off steep, slumping faces — a genuine safety gain. A covered cement or fertiliser shed, where a drone cannot fly and a camera has no light, is laser-scanner territory. For a single product bay at a quarry, a quick GNSS or total-station pickup is often the most economical answer. ISS routinely uses Leica and Trimble GNSS and total stations, DJI Matrice-class UAVs for aerial capture, and FARO and Leica scanners for close-range work.
What coordinate system and datum will the results use?
Volumetric deliverables are referenced to GDA2020 / MGA2020 by default, or to your established mine grid, with heights reduced to the Australian Height Datum (AHD). This matters more than it sounds. A volume figure is dimensionless, but the surfaces that produced it are not — they have to line up with your previous surveys, your design surfaces and your reconciliation history.
The most common cause of a disputed volume is a datum mismatch: this month's survey on one grid, last month's on another, and the apparent "movement" is just a shift in coordinates rather than real material. Specify your horizontal datum, vertical datum and the base surface to be used up front, and every monthly survey will be directly comparable. ISS confirms all three before mobilising.
How is volume turned into tonnes?
Volume is measured in cubic metres; your reports, royalties and sales are in tonnes. The bridge between them is bulk density — the tonnage factor — and it is where many "the survey is wrong" disputes actually originate.
A volumetric survey delivers an accurate cubic-metre figure. Converting that to tonnage requires multiplying by the in-situ bulk density of the material, which varies with moisture, compaction, particle size and material type. ISS reports the surveyed volume and the surfaces behind it; your metallurgist or technical services team applies the agreed density factor, because they own the sampling and the assay data that establish it. A surveyor who quietly applies their own density assumption is hiding the single largest source of tonnage error. Keep volume and density separate, and audit each on its own.
How often should stockpiles be surveyed?
It depends on the value and turnover of the material. Most Australian mining operations survey saleable stockpiles monthly for reconciliation, aligned to the financial month-end and the inventory cut-off. High-value or fast-moving material may justify fortnightly or weekly surveys; slow-moving long-term stocks may only need quarterly checks.
| Situation | Typical frequency |
|---|---|
| Month-end inventory reconciliation | Monthly |
| High-value or fast-turnover product | Weekly to fortnightly |
| Long-term or strategic stockpiles | Quarterly |
| Pre- and post-shipment / loadout | Per event |
| Bulk earthworks progress claims | Per claim period |
For earthworks and civil projects, volumes are usually measured per progress claim or against a design surface for cut-and-fill verification. The principle is the same as mining: a consistent base surface and datum across every survey is what makes the numbers comparable over time.
Frequently asked questions
How accurate is a drone stockpile volume survey?
A properly controlled drone volumetric survey typically achieves 1-3% volume accuracy on well-defined stockpiles, which meets month-end reconciliation and inventory reporting requirements at most Australian operations. Accuracy drops on fine, wet or steeply shadowed material that the camera struggles to resolve — those cases are where terrestrial laser scanning or a supplementary ground survey earns its place.
Can you survey a stockpile inside a shed or under cover?
Yes — that is a job for terrestrial laser scanning rather than a drone. A scanner such as a FARO or Leica unit captures the full geometry of covered material without needing flight clearance or natural light, and ties the result into your site grid using surveyed control. Bunded chemical stocks, covered cement and fertiliser sheds, and material stored against walls are all standard laser-scan work.
Do volumetric drone surveys need CASA approval?
The operator carries that burden, not you. All commercial UAV work in Australia is regulated by the Civil Aviation Safety Authority under Part 101, and the provider must hold a Remote Operator Certificate (ReOC) with a licensed Remote Pilot. You simply need to engage a certified, insured operator and provide site access, inductions and any aerodrome or airspace context for your location. ISS manages all Part 101 compliance.
Why does my surveyed tonnage differ from my claimed tonnage?
Three usual suspects: the base surface, the bulk density and the datum. If the ground beneath the pile was assumed rather than surveyed, the volume can be well out. If the density factor is wrong, a perfect volume still gives a wrong tonnage. And if this survey and the last sit on different grids or vertical datums, apparent changes can be artefacts of coordinates, not material. A clean reconciliation keeps volume, density and datum auditable and separate.
What deliverables do I receive from a volumetric survey?
A volume report stating the figure and the method, the top and base surfaces used (as LandXML or DWG/DGN), a point cloud (LAS/LAZ) where captured, and an orthomosaic or scan imagery for visual context. Everything is georeferenced to GDA2020 / MGA2020 or your mine grid with heights on AHD, so the data drops straight into your design and reconciliation software.
How long until I get the results?
Field capture is fast — a large ROM pad flies in well under an hour. Processing the surfaces and computing volumes usually takes 4-24 hours depending on data volume and deliverable detail, so most volumetric surveys are delivered within 2-5 business days. Rush turnaround for month-end deadlines is available, typically at a 25-50% premium for after-hours processing.
Request a volumetric survey quote
If your operation depends on accurate stockpile reconciliation, quarry product volumes, waste-dump tracking or bulk-earthworks measurement, a controlled volumetric survey puts defensible numbers in your hands within days — and keeps your surveyors off unstable faces. ISS operates Australia-wide, selects the right method for your site, and delivers in GDA2020 / MGA2020 (or your grid) with full quality reporting and the surfaces behind every figure. Tell us the material, the location and your reporting cycle, and we will scope the work and provide a written quote within 24 hours. Call 0407 057 015 to discuss your next volumetric survey.