Drone topographic surveys, drawn to survey-grade CAD

On open, hard surfaces with properly surveyed ground control, a drone topographic survey typically achieves ±15–25 mm horizontal and ±20–30 mm vertical RMSE at a 1–1.5 cm ground sample distance. Accuracy on grass and soft ground is a little lower because the surface itself is less well defined. We test every job against independent checkpoints that are withheld from processing, and the achieved figures are printed in the survey report.

Price depends on site area and shape, the accuracy and resolution required, how many features are to be drawn, how much ground infill is needed, and any access or airspace constraints. Five hectares of open greenfield with a light feature list is a very different job from five hectares of town centre streets. We quote a fixed fee against a written specification, usually within one working day.

For levels and visible features across open ground, a drone survey is accurate enough for most design purposes and far denser in coverage. A total station is still better for sub-centimetre work, building detail, drainage inverts and anything hidden from above. On many sites the best result comes from combining the two: aerial capture for most of the site and targeted ground observations where they add value.

Photogrammetry cannot see the ground beneath dense canopy, so woodland levels taken from imagery alone are unreliable. Where there is significant tree cover we use, or add, the Zenmuse L2 LiDAR, whose multiple returns reach the ground through gaps in the foliage. Under dense evergreen cover or heavy understorey, we infill with GNSS rover observations to close any remaining gaps.

By default, OSGB36 British National Grid for position and Ordnance Datum Newlyn for height, transformed from ETRS89 using OSTN15 and OSGM15, Ordnance Survey’s definitive transformation. We can also deliver on a site grid or a scale-factor-free engineering grid for setting out, or tie into an existing control network that you supply.

Sites of up to 20 hectares are typically issued within five working days of capture. If your designers need to make a start, the orthomosaic and a preliminary surface can usually be shared within 48 hours. Large or feature-dense sites are programmed individually, and the delivery date is confirmed in the quote.

We need the landowner’s or occupier’s consent to take off and land, and we handle the aviation side ourselves. Skykam operates under a CAA Operational Authorisation in the Specific category, which allows closer working to people and structures than the Open category permits. Where a site falls within an aerodrome Flight Restriction Zone, we obtain the aerodrome’s permission before the flight date.

We don’t fly in rain, and we avoid strong or gusty wind because it degrades image sharpness and positioning, even when the aircraft is rated to fly in it. Bright overcast conditions are ideal for photogrammetry because they remove hard shadows. If a capture window is lost, we move to the next suitable one at no extra cost and confirm any change to the delivery date the same day.

Yes. Survey practices and consultants routinely send us their layer template, block library and coding list, and we draw to it. If you have no standard of your own, we use a clear default based on common UK survey practice and document every layer and block in the report.