When a drone survey wins
The site is large (more than 2 hectares)
Above 2 ha, a drone topographic survey is faster, cheaper, and produces a richer dataset than a walking survey. A 10 ha site that takes a ground team three days takes a drone team a morning, and you get an orthomosaic and point cloud rather than a limited set of spot heights.
The ground is dangerous or inaccessible
Steep slopes, unstable ground, active demolition, live railways, water-logged sites, or cliff faces — anywhere putting a person on the ground is a safety risk. Drones remove the exposure entirely.
You need a complete visual record, not just survey data
A drone delivers an orthomosaic and a point cloud. The orthomosaic becomes a visual reference your whole design team can use, even the ones who do not open CAD. Traditional survey gives you a set of coordinates on a screen.
The project will need progress monitoring
Once you have a baseline drone survey, every subsequent construction monitoring capture aligns on the same CORSnet-corrected grid. Earthworks volumes, structure heights, and pavement condition become trendable over months. Ground survey repeats require a full re-survey each time.
Planning or tender-pack documentation is due
An orthomosaic at 2 cm/pixel, with a residuals report and flight log, is a planning document that holds up to local authority scrutiny. Ground-measured spot heights on a sketch do not.
When a traditional ground survey wins
The site is tiny (under 0.5 hectare) and you need spot heights
A skilled surveyor with a total station will finish a 0.25 ha site in two hours and deliver an AutoCAD drawing the next day. Mobilising a drone for the same job is less efficient.
Everything is indoors or under cover
Drones need sky. Indoor surveys, basement voids, tunnels, or anything under roof cover are better captured with laser scanners (static or mobile).
You need absolute spot heights on specific features
If the deliverable is “the exact height of these 12 manholes to 5 mm accuracy,” a total station on a tripod is still the right tool. A drone gets you to 20-35 mm vertical; a total station gets you to 5 mm.
Cloud, rain, or fog will persist for the whole survey window
Drones are grounded by cloud ceiling and precipitation. If your site has a hard deadline and the forecast is four days of heavy rain, a ground survey still goes ahead; a drone survey slips.
The site is in a flight-restricted zone with no workaround
Drone flight in IAA-restricted airspace (Dublin city centre, near airports, certain heritage zones) requires specific authorisations that can take weeks — check the Irish airspace map before you plan. If you need data tomorrow, a ground team is the practical answer.
The middle ground: often both
Many projects combine methods. The drone provides the orthomosaic and DTM (delivered in Irish coordinate systems); a ground surveyor ties in control to an absolute national datum benchmark; both datasets co-register. This is routinely done on infrastructure projects.
Not sure which fits? Send us the project brief and site boundary. If a ground survey is genuinely the better choice we will say so, and point you to a ground survey partner. A drone service does not sell every customer a drone.