Drones Set the Stage for Low-Cost, Precise Construction with 3DR App
Michael Molitch-Hou posted on April 30, 2018 | | 5225 views

It’s quickly becoming clear that drones can act as affordable tools for collecting data about a construction site. As their applications evolve, it’s also becoming apparent that drones may profoundly disrupt the surveying field that the architecture, engineering and construction (AEC) industry has grown accustomed to.

The latest indicator of this trend is the 3DR GCP app, just announced by low-cost drone pioneer 3DR. The software relies on Trimble’s inexpensive Catalyst hardware to determine ground control points (GCPs), which are necessary for maintaining precision in a wide array of construction operations, on site. In turn, the app might just make the use of pricey surveying hardware obsolete.

To learn more, we spoke to 3DR CEO Chris Anderson.

What Is Catalyst?

Trimble spearheaded global positioning technology (GPS) in the late 1970s, eventually establishing itself as a leader in a variety of fields. In 1992, the company developed real-time kinematic (RTK) technology capable of providing moment-by-moment GPS information, enabling surveyors to perform topographic mapping and other tasks.

This early Global Navigation Satellite System (GNSS) ultimately made Trimble a leader in surveying hardware. Now, such RTK units are regularly used by surveyors brought onto construction sites for a number of tasks. The only issue is that, not only does the cost of the equipment range in the tens of thousands of dollars, but it also requires a trained expert to operate. The invention of the smartphone, however, came into the picture to change all of that.

Referencing Andreessen Horowitz founder Marc Andreessen’s now famous Wall Street Journal op-ed, 3DR’s Chris Anderson explained that, even in the AEC industry, “software eats the world”. Just as e-readers often supplant physical books; streaming services have replaced DVDs, CDs and cable boxes; and smartphones have ousted just about every piece of hardware, new software and cheaper hardware is replacing traditional surveying tools.

“Trimble, to their credit, could see this trend and asked themselves what if these expensive RTK units could become an app on a phone?” Anderson explained. “What if all of the computing elements and wireless direction could be done on a phone and all you would need is a very low-cost antenna that you would plug into the phone? That’s exactly what they did with their Catalyst product.”

With a Catalyst subscription, users can plug a Trimble DA1 antenna into an android device to use third-party apps, such as 3DR GCP. (Image courtesy of 3DR.)
With a Catalyst subscription, users can plug a Trimble DA1 antenna into an android device to use third-party apps, such as 3DR GCP. (Image courtesy of 3DR.)

Released in July, 2017, Catalyst relies on a roughly $350 Trimble DA1 antenna to bring high-precision GNSS to Android devices. Whereas your Google Maps app can tell you where you are within a few meters, Catalyst can do so down to the meter, submeter, decimeter or centimeter, depending on your subscription plan.

“It’s a classic innovator’s dilemma,” Anderson said.“They could release a $300 antenna that competes with a $30,000 device that they also sell. Somebody’s going to do it, so they might as well do it to themselves and see how it goes.”

Setting GCPs from a Smartphone

Trimble has also released the software development kit (SDK) for Catalyst, giving developers the opportunity to create their own Catalyst apps. 3DR is among the first to do so with its 3DR GCP app, which also happens to be 3DR’s first product with Trimble.

In surveying a project, a trained surveyor will establish markers, control points, that use longitudinal and latitudinal coordinates throughout the site. This makes it possible to construct the building accurately, in relation to these markers.

When it comes to the use of drones, GCPs establish real-world reference points for data captured by the vehicle in flight. The photos or videos taken during a drone flight can then be photogrammetrically stitched together based off of GCPs.

“Having these precise points on a site is how everything else [on the project] becomes equally precise,” Anderson said. “Everything is referenced off that. When you fly drones, drone data is also referenced off those ground control points. Without that level of precision, you don’t really know exactly where everything is.”

Until now, establishing GCPs on a construction site would require the aforementioned RTK units, run by expert surveyors. With the 3DR GCP app, however, it’s possible to simply fly a drone above the site to establish GCPs. More than that, to recapture control points as a project progresses, in the case that an old marker has been covered in dirt, for instance, the project team can simply fly the drone out once again.

“We want people to shoot more GCPs and shoot them more often to make sure they’re up to date,” Anderson continued. “That’s expensive and time consuming. If we can make that as easy as flying a drone itself, which is to say pushing a button on a phone, then the entire system works better and becomes more precise. We’re trying to encourage the notion of constant digitization.”

While GCPs are essential for drone mapping, they can also be used by surveyors to lay out a project on the ground. As construction has become increasingly digitized, surveyors have come to rely on total stations, which measure the distance between a retroreflector held by the surveyor and the station itself, to precisely map out a project’s 3D models onto the physical site.

With GCPs taken by drones, this process can be performed more quickly, easily and affordably. The total station is placed on top of a GCP and the surveyor can establish other areas of the project in relationship to those points, without the need for manually created control points.

Democratizing Construction

Before establishing 3DR, Anderson worked with the open source drone community to develop the infrastructure and operating system for the technology. This technology was then turned over to the Linux Foundation, while 3DR moved from manufacturing its drones—something that could now be tackled for even cheaper by companies like DJI—to developing software for drones.

“Overall, what we’re trying to do is automate functions of construction. The more you automate, the cheaper, the safer, the more accurate and the more often you do it,” Anderson said.With 3DR’s Site Scan software, the company has essentially automated site mapping, since a drone can collect site data at the push of a button. Now, with GCP, it’s possible to create control points automatically, without expensive technology or specialized expertise.

“This notion of democratizing these techniques and these tools is a very classic strategy that companies do to disrupt and improve industries,” Anderson said.“Once you make it so that something is cheap and easy to do, more people do it and they do it more often. This is just a long trend we’re following—turning advanced technologies and advanced skills into things that anybody can do with a phone.”

3DR GCP is available with a subscription to Site Scan and requires a Trimble DA1 antenna and Catalyst subscription. To learn more about the 3DR GCP app, visit the company’s website. To learn more about Trimble Catalyst, visit the Catalyst website.


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