When Chris Kahn arrives by helicopter on the island of Barbuda, in the Caribbean, he sees reef-lined beaches, meadows, marshes, and construction underway on a private club consisting of more than 200 luxury family homes, a world-class golf course, and other amenities. Construction on the project, by Discovery Land Management, will last at least another 10 years, said Kahn, who began working on it in late 2019. The island, which can also be reached by ferry or small plane, is 15 miles long and has a local population of about 1,500 people.
The biggest challenge for the project was the total lack of internet connectivity on the island, except for satellite communication at basecamp. A consultant who designed the golf course irrigation layout had attended many meetings for the project in which the participants discussed in vain how to coordinate their work without an internet connection, a problem that a few engineering firms had also been unable to solve. So, he suggested that they turn to Kahn, with whom he had already worked closely. Discovery Land Management hired Kahn, founder and owner of AlphaRTK, to provide a common operating picture for the teams of surveyors, architects, planners, construction workers and landscapers building the resort and the golf course.
RTK UHF Base Station
Kahn proposed they build their own RTK UHF base station. “You can get about a seven-mile line of sight out of UHF and with repeater radios we can extend that, which is what we eventually did,” Kahn explained. So, he put the base station where the project had an internet connection and relayed the UHF signal from there. He gave the teams Eos Arrow Gold GNSS receivers, which have a UHF plug on the side, with Satel UHF radios. “It works like a charm,” he said. He also set up for the project an ESRI ArcGIS Online account, which now hosts all its maps and data.
“They’re doing a lot of earthwork that needs survey-grade accuracy but does not legally require a survey,” Kahn pointed out. Starting in about 2010, he explained, RTK accuracy began to explode for geographic information systems (GIS) and unmanned aerial systems (UAS). “It’s accelerating,” he said. This has greatly increased opportunities for high accuracy data collection beyond traditional surveying tasks such as boundary surveying. “My niche, and one of the places where there’s a lot of pain, is this interoperability between projects that have surveyors and landscape architects and all sorts of folks in subject matter expertise that are trying to come together to build something.”
Like the rovers, the base station contains an Eos Arrow Gold, with a 35-watt Satel UHF output. Project staff and contractors can connect to it with any device that can accept that UHF protocol. Their rovers are set up to work with ESRI ArcGIS Field Maps, so that workflow is very smooth, Kahn said. The project started where they began to build the golf course, at a worksite seven miles away from the base station, across open water. Kahn then installed a UHF repeater antenna there and additional ones as construction moved inland.
The island is relatively flat, but the sand dunes are quite large. Therefore, to enable the line of sight that UHF requires, Kahn had to install the antennas for the repeaters as high as possible. For one, he used a whip antenna on top of a 15-foot telescopic mast on top of a 20-ft high deck. A repeater antenna costs about $2,500 and takes a few hours to install. “It is fairly old technology,” he said. “I tend to look for an easy button and string together inexpensive ways to do things fairly rapidly.”
UAS Photogrammetry
The project covers 2,500 acres at two locations. While traditional surveyors are working on the project for building construction, their speed is too slow for the crews doing earthwork, particularly on the golf course. This involves pushing sand around, dredging lagoons, and building the course, which requires taking many elevations very rapidly. To speed things up, Kahn decided to use UAS to fly frequent photogrammetry collections. He began by installing ground control points, surveyed them, and put them around the construction sites. He then trained the laborers on the project to conduct high-accuracy, survey-grade workflows using UAS the flight paths of which he programmed.
All the laborers need to do is launch the UAS and, after each flight, extract the SD memory card and upload the data to a shared directory. “They don’t even have to put the props on anymore because they just fold out,” Kahn said. He processes the data and publishes the aerial photogrammetry into the project maps. The next day, everyone on the project has access to survey-grade accurate aerial imagery and a map.
“How frequently they fly them depends on how much activity is going on at the various sites,” Kahn said. “That turnaround time can be as short as a few hours if they need it, between them flying it, uploading it for me, and having it back in their maps. Everything has sub-inch positional accuracy. When they zoom into some of the foundation pilings on the homes, they’re aligning perfectly.”
Survey-Accurate GIS
Project managers need GIS to see everything — survey, landscape design, architectural design, engineering design — in a common operational picture, which they were not able to do prior to Kahn joining the project. “I was looking at email threads that were 45 messages long, with two dozen people on three different continents, talking about where something’s located and referencing something else, with many civil drawings attached as PDFs — one from the landscape architect, one from survey, one from a civil engineer. They were saying, ‘Well, this doesn’t look like it matches.’ I was brought in to make it all one pane of glass.” That requires overlaying survey-grade accurate architectural and engineering information on the GIS information.
“That’s where you run into this niche area in which I work that often surveyors don’t fully understand,” said Kahn. “In the United States, there are civil engineering surveyors and design-build shops that include geospatial, though it is not commonplace. Outside of the United States, it is rare.”
The rovers for GIS data collection are sub-centimeter accurate, as are the ground control point targets that Kahn installed for the UAS workflows. Workflows were designed for simplicity, allowing laborers to reliably perform UAS and GNSS data collection.
ESRI ArcGIS Field Maps is well suited for this project because it works offline. As they walk around the site and try to understand what they will build, planners, architects and engineers can see the most current maps on their phones, rather than having to consult PDFs or paper.
“I had to do a lot of work with their engineering firm, though, to get their 3D civil drawings to interact with GIS,” Kahn recalled. “Now, all the line work coming from engineering is perfectly aligned, and all field adjustments made by construction are real-time updated in the design drawings. You can see how accurate this GIS is. Everything is perfectly placed, and these are data coming from four different places: GIS, UAS, engineering design, and survey. Everything is aligned within one to two centimeters.”
With golf course building, “design is a suggestion,” Kahn said, and many changes are made in the field. “In fact, the pace of ‘field adjustments’ was a crucial reason I was brought in. Engineers cannot wait a year for an as-built drawing set to be delivered.”
Cut-and-Fill
This workflow streamlines the many cut-and-fill operations involved in the project. “Coco Point is a good example,” Kahn said, “because some of the lots there are completed.” Zooming into one of the completed lots, he can see the nine-foot grade for which one construction company is responsible and the 11-foot grade for which another construction company is responsible. “It’s important for them to know those two grades because of cost; it’s very expensive to bring fill in here. So, as they’re doing these drone flights, they have dashboards that show them how much fill they need to bring in.”
The common operational picture enables project managers to optimize the cut-and-fill transfers. The golf course was particularly challenging because it is in a very swampy area, making it difficult to move the dredging equipment. So, they asked Kahn to design the path for the trucks and determine how much fill they would extract out of these lagoons. “I knew they needed this much to meet design on the green and could get this much out of the lagoon,” he said. “It was very helpful for them procedurally with the planning.”
Challenging Environment
The environment on the island is challenging. “It was wild,” Kahn recalled. “Nothing but wild donkeys and enormous boars, which I really learned to avoid after a while. It is mostly wetlands, so it is hard to get around.” A construction manager told him: “Chris, I’ve led projects on every continent, but this place is the [expletive] moon.”
The challenging environment and the lack of internet connectivity make the system that Kahn set up particularly helpful, because it provides accurate data quickly and with a streamlined workflow. “The big story here is that common operational picture,” Kahn said. “It’s taking the best tools of the GIS/geospatial world — such as RTK and UAS. They must be accurate, work offline, and be very easy and fast. You must maintain that accuracy so that the surveyors who work on this project aren’t going to yell and scream.”
The project also requires building and maintaining utilities — water, gas, sewer, stormwater, electric, and telecom — which are all in underground plastic pipes and are often not placed as designed. “Doing the digital ‘as building’ up front, as it goes in the ground,” Kahn said, “saves time and money down the road.” Additionally, the turnover of people who work on these projects, including managers, is high, so institutional knowledge is constantly lost. “Utilities in the United States have a fairly stable workforce, but in the resort world, everything’s plastic and sand,” said Kahn. “The high turnover and the low institutional knowledge make it even more important to have a true digital twin.”
