Robot dogs and ground robots for site scanning and progress capture

A robot dog on a building site is not a novelty act; it is a tripod that walks. The hard part of scanning a building under construction was never the scanner, it was carrying it to two hundred stations every week and setting it down in the same places. A quadruped does that on its own, and the data it brings back is the first kind of site record that is the same every time it is taken.

What they are

A ground robot for capture is a self-navigating carrier with a sensor on top: a four-legged quadruped for stairs, rubble and door thresholds, or a wheeled or tracked rover for flat slabs and yards. The robot looks after walking and not falling; the payload (a laser scanner, a 360° camera, sometimes both) looks after measuring. In 2020 the scanner makers began shipping the two as one product, with the robot carrying a survey-grade scanner and the scanner’s software driving the robot from station to station, and the combination has since gone into regular use on large projects.

1,000+

Quadrupeds of one make reported in the field by 2021, many on construction sites

~$74,500

A reported price for a quadruped with a survey scanner on its back

weekly

The usual rhythm: the same route, the same stations, every week

0 GNSS

Satellites needed indoors. The robot positions itself from what it sees

The route, the stations, the schedule

The animation at the top is the whole method. Somebody walks the robot through the floor once, with the controller, and it records the route and the places where it should stop. From then on it repeats the mission on its own: walks to station one, stands still, scans, walks to station two. If a pallet has appeared on the route it steps round it; if a wall has gone up it finds another way or reports that it cannot. The scans from each visit are taken from the same places, so the comparison between weeks is a subtraction rather than a search.

1. Once

   Record the route

   A person drives the robot through the space; it maps as it goes and remembers the stations. Control points on the floor tie the map to project coordinates.

2. Each visit

   Walk and scan

   The robot repeats the mission on a schedule or on command, scanning at every station. An operator can watch remotely and does not need to be on the floor.

3. Same day

   Register and compare

   The scans are joined into one cloud in project coordinates and compared with the design model and with the previous visit.

4. Ongoing

   Act on the differences

   Elements built, elements missing, elements out of tolerance, each flagged for the people who need to know, with the scan as evidence.

Quadrupeds, rovers and the rest

• Quadruped (robot dog)Four legs: stairs, kerbs, rubble, thresholds, a floor with the deck still open. The usual choice inside a building under construction, where nothing is flat yet. Hours of battery; swaps its own.indoors and rough ground · $75,000–150,000 with scanner
• Wheeled or tracked roverCheaper, carries more, runs longer, and cannot climb a stair. Fine on finished slabs, in yards, along a pipe rack, through a warehouse. Some print layout on the slab as they go.flat ground · $20,000–80,000 with sensors
• The human alternativeA handheld SLAM scanner carried by a person on the same route, every week. Less repeatable, far cheaper, and the right answer on a site that is not large enough to keep a robot busy.anywhere · $20,000–60,000

What rides on the back

The robot is the legs; what it carries decides what the site gets.

Terrestrial laser scanner

Millimetres, colour, and a full dome at each station. The survey-grade option, and the heaviest and dearest. The scanner's own software plans the stations and registers the scans.

Spinning LiDAR with SLAM

A continuous cloud as the robot walks, centimetre-level, no stations needed. Faster and less precise; good enough for progress, not for as-built tolerance checks.

360° camera

A walkthrough the whole team can open, with the images placed on the plan. Visual, not measured, unless the images are also run through photogrammetry.

Thermal, gas, acoustic sensors

Beyond geometry: heat on a panel, a leak, a running pump. The same route logic applies: measure the same places on every visit and compare.

What the data is used for

Three things, in order of how often they are done. Progress: what has been built since last week, by element, against the programme. Verification: what has been built where it should be, within tolerance, against the design model, caught while the trade is still on the floor. And the record: an as-built scan of every floor at every stage, for the handover and for the arguments afterwards. An architecture practice testing a quadruped on a London site in 2020 ran it weekly on the same pre-mapped missions and compared each visit with the BIM model and the programme, which is the same loop the scanner makers built their products around.

The robot’s own position is a product in its own right: where it is on the site, in real time, on the same map as the trucks and the excavators. Clarity’s live tracking shows anything that reports its position on the site map, and plays back where it went.

What they cost and when they pay

A quadruped with a survey scanner was reported at about $74,500 in 2021; the robot alone is in the tens of thousands, the scanner is the rest, and software, support and a spare battery or two come on top. Rovers with lighter sensors are a fraction of that. Against it: a scanning technician’s weekly visit to a large site for a year, with the stations never quite in the same place, or a site that goes unscanned because nobody has the time. The arithmetic works on a big project with many floors and a long programme, and does not on a small one, which is why the robots are on hospitals and data centres rather than houses.

Robot against drone

On a large project the answer is both, tied to the same control: the drone for the earthworks, the stockpiles, the structure rising and the site as a whole, the robot for what is happening inside it. The drones page covers the first; the scanners page explains what the second carries.