Why You Want a Total Station On Site When Scanning
A laser scanner produces geometry that is accurate within itself and floating in its own coordinate system. A total station is what ties that geometry to the real world. Bring both to site and you get scan data that can be compared against a design model, checked independently, and matched to a scan you take two years from now. Bring only the scanner and you get a very detailed cloud that does not line up with anything.
Here is what a total station adds, and how the two work together in practice.
Control: what it means and why it matters
Control is a set of known points, measured precisely, that everything else references.
When you register scans to each other alone, errors accumulate. Each alignment carries a small uncertainty, and across a long building those add up, so the far end of your cloud drifts relative to the near end. It is internally consistent and progressively wrong.
Control fixes that. Place targets through the space, shoot them with the total station, and register scans to those known coordinates instead of only to each other. Error stops accumulating, because every scan is tied back to the same reference.
Do that and the cloud sits in real site coordinates. It can be overlaid on the design model, compared against a scan from last month, and handed to another team who can work in the same coordinate system.
Verification: proving the scan rather than assuming it
This is the argument that convinces people.
Registration software reports its own confidence, and that report is not independent. It tells you how well the scans agree with each other, not whether they are right.
With a total station on site you have an external check. Measure the distance between two targets with the total station, then measure the same distance in the registered point cloud. If they agree, you have verified your scan against an independent measurement. If they do not, you have found a problem while you can still do something about it.
You can check levelness the same way, and the elevation of the scan against known site elevations. On any project where the data has to be defended, whether that is a fabrication deliverable or forensic evidence, this is the difference between confidence and hope.
A worked example: scanning a hotel floor
Say you are scanning the first floor of a hotel. Lobby, hallways, stairwells. The client will take the data into Revit for a redesign.
With just a scanner, you capture the space and register it, and it goes to the client sitting in its own coordinates. Their model exists in project coordinates. Somebody now has to align the two by eye, and every subsequent scan has the same problem again.
With a total station on site, the workflow changes:
- Place scan targets through the lobby, hallways and stairwells.
- Shoot the targets with the total station, tying them to project control.
- Use Point Layout in Revit to pick up coordinates at grid intersections, wall corners and columns, and export to a text file that imports into Register360.
- Register the scans to those coordinates. The cloud lands in project coordinates automatically.
- Check target to target distances against the total station measurements to confirm accuracy.
- Check elevation and levelness of the scan against known values.
The client receives data that drops into their model with no alignment work. Stairwells, which are the hardest part of any multi level scan to register well, are tied to the same control as everything else.
What else the total station is doing while it is there
Once the instrument is on site, it earns its keep beyond control.
- Layout. Scanners record what exists. If you also need to mark positions from a design, only the total station does that.
- Verticality checks on formwork and structures, measuring to a prism.
- Spot checks of specific critical dimensions, faster than scanning and processing.
- Establishing control that later trades and later scans will reference.
The full comparison of scanners and total stations
When you can skip it
Not every job needs one, and it is worth being clear about that.
A single room, a small building captured from a handful of setups, or a scan where the deliverable is visual rather than dimensional will usually be fine on scan to scan registration alone. Modern instruments in the Leica RTC series pre-register in the field and hold up well over short runs.
Bring a total station when: the site is large or has multiple floors, the data must tie to project coordinates, the deliverable feeds fabrication, you will rescan the same site over time to compare, or the data may be challenged.
Total stations worth having on a scanning job
The Leica iCON iCB70 is a strong fit for keeping tight project tolerance. It measures to a prism, performs verticality checks on formwork and structures, and runs iCON build with the build plus onboard software. A 5 inch color touchscreen and full numeric keyboard, FineFocus telescope, 1, 2 and 5 arc second angular accuracy options, prism and reflectorless measurement, Bluetooth and WLAN, mobile data as an option, and an IP66 rating for real site conditions.
For layout and as-built checks handled by one person, the Leica iCR70 and iCR80 robotic total stations let you level the instrument and work from the pole rather than standing behind it. That matters on a scanning job, where the same person is often running both instruments. The iCR80 offers longer reflectorless range, the iCR70 covers most building work.
See all robotic total stations
Related: Robotic total stations and job speed | A closer look at the iCB70 and iCT30
Rent both for the project
If you scan a few times a year, renting both instruments for the duration of a project is usually cheaper than owning either. Both ship calibrated as complete working kits, anywhere in the 50 states.
