Cut and fill you can check
Earthworks quantities come down to comparing surfaces: what was there, what is there now and what the design says. A drone gives you the middle one often, cheaply and without crews on the slopes.
Three surfaces and the differences between them
Every cut/fill calculation compares two surfaces. Original ground is the site before work, ideally from a topographic survey or a baseline flight. Current ground comes from the latest flight. Design is the engineer's finished grade, subgrade or pad elevations, usually supplied as a LandXML surface or a DWG with a TIN.
Current minus original gives what has been moved so far. Design minus current gives what is left, as a colour map of cut and fill and a quantity table by area. Repeated through the job, those numbers support progress claims, haul planning and the final reconciliation.
Earthworks is where small vertical errors turn into large quantities. A consistent vertical shift across a big area is a real volume, so control and checkpoints are not optional here. Get the surfaces right and the drone becomes the quickest way to know, every week, how far the job has moved.
For subdivision and lot grading, the same method checks lot pads and road subgrade against the grading plan before the surveyor's final certification. See land development.
How an earthworks job runs
Get the design surface
Ask the civil engineer for the grading surface in the project coordinate system, with a note on whether it is finished grade or subgrade. Subgrade is what the machines cut to.
Fly the baseline
Before stripping, if possible. Topsoil strip depth and trees affect the original surface; LiDAR helps on vegetated sites.
Set permanent control
Marks outside the grading limits so they survive the job, surveyed in the project system.
Fly on a cadence
Weekly, biweekly or at claim dates, with the same flight plan each time.
Compare and report
Cut/fill maps, quantities by zone, and the method, surfaces and dates used.
Reconcile
At completion, final surface against design and original, with the quantity trail from every flight kept in the project record.
Where earthworks numbers go wrong
Finished grade compared to subgrade
Comparing a flight to the finished surface instead of subgrade overstates the fill still needed by the thickness of the pavement or topsoil.
Datum mismatch
Design drawings in an older vertical datum and a flight in a newer one differ by a steady offset. Across a site that is a large false quantity.
Swell and shrink ignored
Bank, loose and compacted volumes differ. A truck count will not match an in-place survey.
Vegetation counted as ground
Grass, brush and silt fences lift a photogrammetric surface.
Equipment in the model
Excavators and trucks become false fill.
Who needs the quantities
Civil engineer
- They need from you
- Current surfaces to check grades and drainage.
- You need from them
- The design surface, tolerance and which layer it represents.
- On the DroneLink record
- Design and flight surfaces kept together in the project record.
Earthworks contractor
- They need from you
- Quantities for claims and haul planning.
- You need from them
- Their claim dates and zones.
- On the DroneLink record
- Reports by zone at each flight, with the method stated.
Owner's representative
- They need from you
- Independent numbers to review claims.
- You need from them
- Agreement on who commissions the flights.
- On the DroneLink record
- The same report set, visible to both sides by link.
Surveyor
- They need from you
- To set control and stake out, and sometimes to certify final grades.
- You need from them
- Control coordinates and their sign-off requirements.
- On the DroneLink record
- Control and checkpoint results shared in the record.
Choosing the method
| Need | Drone | Ground GNSS or total station |
|---|---|---|
| Large open areas, frequent updates | Fast, full coverage | Slow, sparse points |
| Exact elevations at specific points | Good with control | The better tool |
| Trenches, narrow cuts, under structures | Limited view | Better |
| Legal certification of grades | Supports the surveyor | Surveyor signs |
| Crew safety on slopes and near equipment | Off the slopes | Crew on site |
What to have ready
- The design surface from the engineer, as LandXML or DWG, with a note on finished grade versus subgrade and the pavement or topsoil section thickness.
- The project coordinate system and vertical datum, confirmed by the surveyor. See accuracy.
- An original ground surface: a pre-construction topographic survey, or book a baseline flight before stripping. On treed sites, ask about LiDAR.
- Zones or phases you want quantities split into, drawn on a site plan.
- Your claim or reporting dates, so flights land the day before, not the day after. Pair with construction progress visits if you already fly the site.
- A site contact who can hold equipment at a break and confirm safe areas to land. See preparing a site for a flight.
Questions
How do you calculate cut and fill with a drone?
A drone flight produces a current ground surface. Software compares it with the original ground and the design surface, and reports the volume to cut and to fill by area. Results depend on control, filtering and using the right design surface.
What file do I need from my engineer for cut and fill?
Usually a LandXML surface or a DWG with a triangulated surface of the design grades, in the project coordinate system. Ask whether it is finished grade or subgrade.
How accurate is drone cut and fill?
With RTK or PPK, ground control and checkpoints on hard ground, vertical accuracy is typically a few centimetres as general industry knowledge. Vegetation, equipment and datum errors cause more problems than the drone itself.
Can drone surveys be used for earthworks progress claims?
Many contractors and owners use them to support claims, because both sides can review the same dated surfaces. The contract decides what measurement method is accepted, so agree it early.
What is the difference between bank, loose and compacted volume?
Bank volume is material in place before excavation. Loose volume is larger after digging, and compacted volume is smaller once placed and compacted. Drone surveys measure in-place volumes.
Can the drone replace my surveyor on an earthworks job?
No. Surveyors set control, stake out and certify. The drone gives frequent full-site surfaces that make their work and the contractor's claims faster to check.
Will I be able to see cut and fill in a browser?
Cut/fill calculated in the browser is coming in the DroneLink site viewer. Today you receive maps, quantity reports and surfaces as files.
Tell us about your Toronto site.
An address and what you need is enough to start. We reply with what it will take, who will fly it and when.