How to choose a survey, and what to ask for
Two quotes for the same building can differ a lot, and a cheaper one is sometimes the right call. The difference usually comes down to four things, and we can guide you on which ones matter for your project.
Accuracy
A survey to a local accuracy of 10–30 mm is quicker than one to 3–5 mm. Both are valid. Budget will often decide it, and for a simple building that can be the right call. For a historic church façade the difference is real, so bear that in mind before choosing on price.
Just as important is control: a properly controlled survey ties the whole site into one framework, from the building to the topography and the buried services, so small errors don’t build up from one side of the site to the other. Without control, a survey can still come out fine. The trouble is that nothing shows whether it has: each part can look right on its own and still drift across the site, with walls that don’t meet, levels that don’t tie in, or a drain that’s off line by the time it reaches the road. If it has drifted, you usually find out when the design is set out on site. We can help you make that call.
Measured or assumed
Not everything on a drawing is always measured. Wall thicknesses, rooms without access and roof detail are sometimes assumed, and walls can be drawn square when they aren’t. On a drawing, assumed detail looks exactly like measured detail, until someone opens up a wall. Our survey statement tells you which is which.
Checking
Closing the loop back to the first station is how errors get found. Skip it and nothing on the drawing tells you something is wrong. It shows up on site, when it’s expensive. We close the loop and check the figures as standard.
Who is on site
A trained field surveyor carries out every survey, with a senior surveyor behind each job. With today’s mobile scanning, the data is checked before we leave site, and the office can review it remotely while we’re still there, so gaps can be picked up on the day rather than needing a return visit. Our surveyors also see the things a design will trip over: a drain that doesn’t line up, a wall that isn’t square.
- Controlled: the whole site in one framework. Closing the loop shows how well it fits.
- Without control: it may be close, but the error can grow across the site, and nothing on the drawing shows how far it’s out.
Local or global? An accuracy figure on its own doesn’t tell you much. Local accuracy is how well nearby points agree, for example within a room. Global accuracy is how well everything agrees across the whole site. A survey quoted at 10 mm room by room might hold across the site, or might not, and without control nothing shows which. If a quote gives a single figure, ask whether it’s local or global, and how it was checked.
A quicker survey is usually fine for
- Early feasibility and massing studies
- Estimating floor areas for a sales brochure
- Internal layouts where nothing structural changes
- Sites where the design has plenty of room to move
Pay for accuracy when
- You are building on or close to a boundary
- Levels drive drainage, access or flood design
- New work has to fit existing structure or services
- Fabrication or prefabricated parts depend on the dimensions
Scale guide: measured building surveys
| Drawing scale | Capture method |
|---|---|
| 1:100 | SLAM may be appropriate |
| 1:50 | Likely to require tripod-mounted HDS scanning |
| Other scales | On request: tell us the scale and we'll advise |
SLAM: handheld mobile scanning. HDS: high-definition laser scanning from a tripod, set up on survey control.
What to ask any surveyor for
Ask any surveyor four things: what specification is it to, is the accuracy local or global, how was it controlled, and what was assumed? If the answers aren’t written down, you can’t know what you’re relying on.
- The right method (SLAM or tripod-mounted HDS)
- Appropriate survey control
- Grade of accuracy
- Scale suitability
- 3D model level of detail (LOD)
- Clear advice on limitations
- Outputs that match the agreed specification
Our team has been surveying buildings since 1989.
Your survey is the foundation of your design. Everything that follows, from planning drawings to setting out on site, is built on it. So compare what each quote includes, not just the price: the specification, the control, and what is measured rather than assumed. If a cheaper survey is right for your project, we’ll say so.
If a quicker survey suits your project, we’ll tell you. Already have a survey? You don’t want to find out it wasn’t good enough once the design is built on it. If you’re not sure, send it over and we’ll give you a straight view. If it’s fine, we’ll tell you.
Try itSurvey control: set up the instrument for confidence
Survey control: set up the instrument for confidence
In a survey control environment, which means longer on site, the instrument has to know where it is before a single point is measured. The standard topo set-up is over a nail: centre the crosshair on it, then steady the bubble. Or set up anywhere, level, and fix the station by resection, turning the telescope onto known targets: three fix it, a fourth is the check. Either way takes care, and care takes time.
Ready. Click the dial to start, then move the mouse, drag on a touch screen, or use the arrow keys.
- Centre over the nail
- –
- Level the instrument
- –
A toy, not a survey instrument.
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