There are advantages in knowing where everyone on your jobsite is — especially large jobsites, where workers can be a long way from help if there’s an incident. A new tracking method that is similar in concept to the Global Positioning System (GPS) might be one way to prevent incidents or to respond quickly when someone is hurt.
The GPS could likely do the job, but once the walls are up and the roof goes on, the signals from GPS satellites stop.
There have been attempts to provide indoor positioning services using off-Cthe-shelf technologies like Wi-Fi or Bluetooth. Results have been mixed.
But a start-up based in Cambridge, Mass., has devised an indoor positioning system that uses local radio beacons, or "anchors" that are located within the building under construction.
Redpoint Positioning Corp. uses radio technology called Ultra-Wideband, or UWB. The company selected it because it enables more precise location than Wi-Fi or Bluetooth.
The idea is the same as GPS. In fact, the company uses the phrase "indoor GPS" in its literature.
GPS is a system of satellites in very precise orbits. Those satellites (there are now 31 of them) continuously transmit their current time and position. A GPS receiver on the ground monitors multiple satellites and calculates its exact position. To do that, at least four satellites must be in view of the receiver, which means the system works well if the receiver is in an open location. But on a construction site, as the building is enclosed, a different system is needed. That’s where Real-Time Location Systems (RTLS) come into play.
Redpoint’s system uses radio anchors that are located within the building under construction. Company vice-president Jonathan Horne described the system in a recent interview.
The anchors, he said, send out precise timing signals that are picked up by tags worn by workers. The tags, about the size of a standard security badge, can then compute the worker’s location in three dimensions to within 20 centimetres.
As the building goes up, more anchors are added at pre-planned locations, so tags are always able to pick up the radio signals.
Horne said worker safety was one area of prime interest as the product was being developed. The system can alert the worker and their supervisor if they are in a dangerous situation.
"You may have dozens of people on a site," Horne said, "but only a few of them are to be working in confined spaces. So we can identify that space — maybe a crawlspace inside a building — and mark that as a zone that requires that a worker has the credentials to get in there. If somebody without that credential goes into that space, we can alert both worker and supervisor."
The tags can be associated with a single worker, or a single trade. So a supervisor can look at their tablet or smartphone and know how many workers the electrical subcontractor has on the job and where they are.
Tags can be worn by workers, or attached to a piece of equipment. The anchors are placed in pre-planned locations and are powered either by batteries or by connecting them to a main power supply. The anchors are connected to a data network so that information about tag locations can be captured and stored on a server. The server can be somewhere on the jobsite, in an adjacent trailer, or hosted in the cloud. The server can be accessed from a desktop computer located in the site office, or from tablets or smartphones carried by supervisors.
The system can also be used to put a "geo-fence" around an area where equipment is parked. So the little skid-steer tractors that can be seen bustling around many jobsites, can be parked inside the fence, along with a scissor-lift, perhaps, or a compressor. If the tractor is moved outside the fenced area, the system will spot it and will tell the foreman whether or not it’s being driven by the approved operator.
Horne said that building information modeling (BIM) systems complement the Redpoint system.
"When you’re using BIM, you’ve got your building model, and you can see in real time where you are in the model," he said. "Maybe you’ve got a thousand PDFs for your structure, (but) when you’re in a corner of the seventh floor, for example, we can show you only the handful of PDFs that are relevant to you in that spot.
"Similarly, when you’re doing your punch-list and you’ve found some damaged drywall you can take a photo of that with your phone and it’s geo-tagged automatically. The photo is placed in the correct place in the BIM model."
Safety is a subject that Horne returned to several times during the interview. On geo-fencing, he said the system can geo-fence dangerous areas "whether it’s an exposed ledge, or a confined space, or an elevator core where nobody’s supposed to be working, or an electrical closet or lifting operations overhead. We can identify those hazardous areas and alert workers and supervisors."
The badge tags contain a battery. There is also a button that, when pressed, sounds a loud alarm. So if a worker falls, they can hold down the button to call for help. The Redpoint system isn’t a commercial product yet, although Horne said he expects that the system will be brought to market in the second half of this year.