| Instrument | Accuracy | Use For |
|---|---|---|
| Robotic total station (prism) | ± 1 mm + 1.5 ppm | Building layout, bolts, steel |
| Total station (reflectorless) | ± 2 mm + 2 ppm | As-builts only — never layout |
| GNSS RTK fixed (local base) | ± 8–10 mm H / ± 15–20 mm V | Earthwork, utilities |
| GNSS RTK fixed (NTRIP) | ± 10–15 mm H / ± 20–25 mm V | Earthwork, topo |
| GNSS Float (NOT FIXED) | ± 200–500 mm H | NEVER stake in float |
| Rotary laser | ± 1.5 mm @ 30 m | Form tops, grading, floors |
Never use reflectorless mode for layout. Never use GNSS for building layout.
| Element | Tolerance |
|---|---|
| Anchor bolt location | ± 3 mm (total station only) |
| Anchor bolt group (bolt-to-bolt) | ± 3 mm |
| Anchor bolt elevation | ± 6 mm |
| Building control lines | ± 3 mm |
| Footing formwork | ± 12 mm |
| Foundation walls | ± 6 mm |
| Column plumb (per storey) | H/500 or 25 mm max |
| Column base plate elevation | ± 3 mm (after shim/grout) |
| Slab-on-grade elevation | ± 12 mm |
| Element | Tolerance |
|---|---|
| Footing location (plan) | ± 50 mm |
| Footing top elevation | +12 / −50 mm |
| Wall / column plumb | 25 mm in 3 m |
| Floor slab thickness | −6 / +12 mm |