Data you can check, in formats you use
Drone mapping is a data source, not a survey. Here is what it can and can't do, what you should receive, and where your stamp stays essential.
A dense, current measurement of the surface
A photogrammetry flight takes hundreds or thousands of overlapping photos. Photogrammetry software matches points between them and reconstructs the surface: an orthomosaic, a digital surface model (DSM), a point cloud and a textured mesh. A LiDAR flight measures distance with a laser and records millions of points, including returns from the ground through gaps in vegetation. Filter the ground points and you get a digital terrain model (DTM) and contours. See how drone mapping works.
What drone data is not: a legal survey, a boundary, a certified topographic plan or an engineering opinion. It does not see through dense canopy the way people assume, it struggles on water, glass and uniform surfaces, and a sharp-looking model can still sit metres away from its true position if it isn't tied to control.
On Vancouver Island DroneLink flights are flown by Elite Drone Solutions, Transport Canada Advanced-certified. Processing is done in-house. Deliverables arrive as standard files on the project record, so the dataset, the flight date and the order stay together.
Pick the sensor for the surface, not the brochure
| Condition | Photogrammetry | LiDAR |
|---|---|---|
| Open ground, stockpiles, pavement | Strong, with colour and texture | Works; often more than needed |
| Vegetated ground | Measures the top of the vegetation | Can reach ground through gaps in canopy |
| Power lines, thin structures | Often missed or smeared | Captured as points |
| Water, glass, snow, uniform roofs | Poor matching, holes and noise | Weak or no returns on water; better on most surfaces |
| Visual deliverable (orthomosaic) | Native output | Needs a camera flown alongside |
| Flight and processing effort | Lower | Higher; strip alignment and classification needed |
Relative, absolute, and the number that matters
Two kinds of accuracy get mixed up. Relative accuracy is how well the model agrees with itself: a distance measured across a stockpile, the slope of a driveway. Absolute accuracy is how close each point sits to its true position in your coordinate system. A model without control can be excellent relatively and poor absolutely. For volumes against a design surface, tie-ins to existing infrastructure or anything that meets another dataset, absolute accuracy is what counts.
The honest way to state accuracy is against independent checkpoints: surveyed points that were not used to build the model. Report the root mean square error horizontally and vertically, the number of checkpoints, and where they were. Checkpoints clustered on one paved lot say little about a sloped, vegetated site. Vertical error is usually larger than horizontal, and it grows on vegetation, steep slopes and the edges of the flight area.
Ground sample distance, the size of one pixel on the ground, is resolution, not accuracy. A two-centimetre pixel does not make a two-centimetre survey. Ask for both numbers, and treat any vendor accuracy figure without checkpoints as a hope, not a measurement.
The ways drone data lets engineers down
No control, no checkpoints
The model looks perfect and is shifted by a metre. Relative measurements may be fine; absolute position is not.
Wrong datum or units
Ellipsoid heights delivered to a team expecting orthometric heights, or a local grid confused with UTM.
Vegetation called ground
A DSM used as a terrain model inflates cut volumes and puts contours on top of the bushes.
Files that don't open
Proprietary project files that need a licence you don't have.
What you should receive
| Deliverable | Format | Opens in |
|---|---|---|
| Orthomosaic | GeoTIFF | QGIS, ArcGIS, AutoCAD, Civil 3D, Google Earth (converted) |
| Surface or terrain model | GeoTIFF | GIS and civil design software |
| Point cloud | LAS / LAZ | Civil 3D, ArcGIS, QGIS, point cloud tools |
| Contours and linework | DXF | AutoCAD, Civil 3D, most CAD |
| 3D mesh | OBJ | 3D and visualization software |
| Volume report | Anyone |
Who signs, and who supplies what
Land surveyor
- They need from you
- Raw and processed data they can check against their own control.
- You need from them
- Control, datum and the scope they will certify.
- On the DroneLink record
- The surveyor stays responsible for anything certified. In Canada that is a BCLS, ALS, OLS or arpenteur-géomètre; in the US a licensed surveyor. In several states, producing topographic maps for design is surveying practice. Check your board.
Civil or geotechnical engineer
- They need from you
- Terrain, drainage and slope data for design and assessment.
- You need from them
- Their accuracy requirement.
- On the DroneLink record
- The engineer decides whether the data is fit for purpose and signs the design. The pilot does not.
Contractor
- They need from you
- Quantities and progress.
- You need from them
- Stable control on site.
- On the DroneLink record
- The same control across flights makes surfaces comparable.
Owner
- They need from you
- One dataset, reused by every consultant.
- You need from them
- Clear rights to use and share.
- On the DroneLink record
- Each consultant gets a link to the same current files on the project record.
Writing a drone mapping order an engineer would sign off
Purpose
Planning, volumes, design topography or as-built. The purpose sets the accuracy.
Accuracy and checks
State the horizontal and vertical target and how it will be checked. The ASPRS Positional Accuracy Standards are a common reference.
Reference frame
Datum, epoch if it matters, geoid, projection, units.
Control
Who sets it, how many points, and how many independent checkpoints.
Sensor and resolution
Photogrammetry or LiDAR, ground sample distance or point density.
Deliverables
Formats, tiling, classification and naming. Viewing and measuring in the browser is coming on the site viewer; today files open in your own software.
Questions
How accurate is drone photogrammetry?
As general industry knowledge, projects flown with RTK or PPK and good ground control typically reach a few centimetres; without control, absolute error can be decimetres to metres. The only way to know is independent checkpoints. See mapping accuracy.
Is drone mapping a legal survey?
No. It produces measurement data. Boundaries and certified plans come from a licensed land surveyor, who may use drone data as one input.
Can a drone see ground under trees?
Photogrammetry can't. LiDAR can reach ground through gaps in the canopy, but dense or low vegetation still limits it.
What is the difference between a DSM and a DTM?
A DSM is the top surface, including buildings, trees and equipment. A DTM is bare ground, with those features removed. Use a DTM for grading and drainage.
What coordinate system should drone data be delivered in?
The one your project uses. Tell us the horizontal and vertical datum, geoid model, projection and units before the flight.
Who is responsible if drone data is wrong in a design?
The professional who relies on it and signs the work decides whether it is fit for purpose, which is why checkpoints matter. Agree responsibilities in the order.
How many ground control points does a drone survey need?
It depends on site size, shape, terrain and whether the aircraft uses RTK or PPK. Compact sites with RTK may need only a few for checking; long corridors and rough terrain need more, spread across the whole area and at the edges. Your surveyor should set the plan.
Can drone data be used for a topographic survey?
It can be the main data source for a topographic plan when a licensed surveyor is in charge, sets control, checks results, edits breaklines and signs the plan. On its own, an unchecked drone surface should be treated as planning data.
Can I get the raw drone photos and flight logs?
Ask for them in the order. Raw imagery and processing details help you check or reprocess the data.
Keep reading
Mapping & surveyAccuracy you can prove →
Mapping & surveyDrone LiDAR for ground you cannot see →
Mapping & surveyOrthomosaics you can measure on →
Knowledge · Mapping & surveyHow drone mapping works →
For builders & contractorsFewer arguments about what was built →
For municipalities & utilitiesPublic assets, measured and on record →
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