Road and sub-base laser scanning to design levels

Yes. We tie the scan to your site control, compare every point on the sub-base with the design surface from your long sections, cross sections or 3D model, and report the deviation across the whole road against the tolerance you work to.

Whatever your specification or adopting authority uses. As an example, Lincolnshire County Council's published estate road tolerances are +10/-30 mm on sub-base surface level and ±6 mm on binder and surface course. Tell us yours and it goes on the report.

The road design (long and cross sections, a 3D design surface or a DWG with levels) and two or three site control points or benchmarks we can tie into. If you only have 2D drawings with levels, we build the design surface from them.

Typically 200 to 300 metres of estate road and footpaths in a half-day, depending on bends, parked plant and how much needs scanning either side. Longer runs are done as a full day.

Rarely. We leapfrog the scanner along the road and work around the gang. Machines can keep working a safe distance away; we only need the section being scanned to be clear while the scanner is turning.

It is the first half of one. If we scan the sub-base and then rescan the finished surface, the difference between the two is the thickness laid at every point. See our tarmac depth surveys page.

For checking a finished layer, usually yes. An RTK GPS rover measures one point at a time and is typically good to around 15 to 30 mm in height in real site conditions, which is coarse against a ±6 mm binder tolerance. A laser scan measures the whole surface kerb to kerb, so a high spot between dips still shows up. Rovers remain the right tool for setting out and day-to-day control, and many sites use both.

Accurate enough to check estate road tolerances, with the margin stated on every report. Our Trimble X9 is specified at 2.3 mm 3D point accuracy at 10 m, and we set up every 15 to 25 m so the surface being checked stays close to the scanner. Each report gives the registration error for that job. If the data is not tight enough for the tolerance, for example because of standing water, we say so and rescan.

Yes. Scanning the formation before the membrane and stone go in confirms the dig depth against design across the whole road, and records the volume taken out. That gives you evidence for the muck-away and a check that the sub-base will finish at the right thickness. Volumes are an extra deliverable, so mention them when you book and they are included in the fixed price.

They are accepted as supporting evidence, but they do not replace the adopting authority's own inspections under your section 38 agreement. The report shows level and deviation across the whole layer against the tolerance you give us, with a dated point cloud the authority's engineer can check. Many contractors use it to prove a layer before calling the inspector, so the inspection becomes a formality rather than a discovery.

Light drizzle, cold and wind are usually fine, but heavy rain and standing water are not. Water lying on a sub-base or binder distorts the readings, and a puddle in a channel hides the very low spot you are trying to find. If the weather is wrong for the check, we rebook at no charge rather than issue a pass we can't stand behind.

Yes. Send the scan or the level data with the road design, the control and your tolerance, and we compare it with design and produce the usual heat-map, pass/fail and cross sections, with no site visit. With rover or total station levels the surface between points is interpolated, and the report says so.