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- What it costs
- Experienced readers
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- In BIMpedia
Surveyors measure the real world. Before design they map the site and existing buildings; during construction they set out where things go and check what was built. Their data is what ties every model to the ground.
| Survey | What you get | Used for |
|---|---|---|
| Control survey | Fixed points with coordinates | The shared reference for everything |
| Topographic survey | Ground levels, features, boundaries | Site design, civil works |
| Measured building survey | Plans, sections of existing buildings | Refurbishment design |
| Laser scan (point cloud) | Millions of measured points | Existing conditions, scan-to-BIM, as-built checks |
| Set-out and as-built checks | Marks on site, measured positions | Building it in the right place, proving it |
What surveyors need from you
- The coordinate system and origin of the project models, agreed in the BEP.
- A clear specification: what to capture, to what accuracy, and in what format.
- Models with correct coordinates so set-out data can come straight from them.
What you need from surveyors
- The registration report and stated accuracy for scans.
- The coordinate reference system and vertical datum, plus the control point list.
- The capture date: existing conditions change.
A refurbishment is designed from a ten-year-old measured survey. On site, a partition that was moved years ago clashes with the new risers; the drawings show it where it used to be.
The coordinator asks for a new laser scan of the floors being refurbished, with a registration report and ±10 mm accuracy, tied to the project's control points. The designers model from it, and the partition is found at stage 2.
You need a scan of an existing plant room before replacing the chillers. List what your brief to the surveyor should specify.
Key takeaways
- Surveyors provide control points, topographic and measured building surveys, point clouds and set-out on site.
- Every survey comes with an accuracy, a date and a coordinate system: record all three.
- Scan-to-BIM models the scanned geometry; the modelled accuracy can't be better than the scan's.
- On site, surveyors set out the building from the model and check what was built against it.
Your notes
Related tool
Coordinate system, base points and survey control, with a best-fit check and IfcMapConversion values.
Open Georeferencing Sheet →