"I think VRS networks are the future," says Rex Webb, survey manager for Lowe Engineers...

Rex Webb has seen it all. From Global Positioning System (GPS) receivers as large as refrigerators in the late 1980s to today's compact, Bluetooth-enabled wireless GPS rover, the survey manager for Lowe Engineers, a full-service engineering, surveying and mapping firm in Atlanta, Ga., has experienced the full spectrum of GPS technology. And now he's gone one step further: Lowe Engineers signed on in November 2004 as subscriber to eGPS Solution Inc.'s (Norcross, Ga.) Trimble Virtual Reference Station (VRS) network in the Atlanta area.

"I think VRS networks are the future," Webb says. "If there was a network like this across the United States, there would be more people using GPS. All you'd need is one rover instead of a rover and a base station."

As a licensee, Lowe Engineers can use their RTK GPS systems 24/7 anywhere in the eGPS network area-now covering 30 percent of the state-for a monthly fee per rover. With the network, survey crews no longer need to set up base stations onsite.

"It's a real benefit to jump from the truck and go straight to work," Webb says. "The amount of time we save is considerable, sometimes an hour a day, sometimes half a day depending on how many sites we're working. Multiply that by a survey crew's rate and it's significant."

Far-ranging Goals

The reference station network was initially set up as a five-station network for Travis Pruitt and Associates' (TP&A, Norcross, Ga.) survey crews. But the innovative surveying firm soon saw a bigger future for VRS networks and created a new company, eGPS Solutions, to build on that future. Lonnie Sears, LS, now heads eGPS; under his leadership the network has grown to its current size and opened to subscribers in July 2004. Today, as word-of-mouth success stories spread, more and more firms like Lowe Engineers are becoming subscribers-or are renting network time on a by-project basis.

All network stations are tied into the existing National Geodetic Survey (NGS) monumentation in northern Georgia (WGS-84). eGPS has already had 10 reference stations accepted into the NGS Continuously Operating Reference Stations (CORS) network (few existed before eGPS), and other stations are in process. Being part of the NGS CORS network will solidify the eGPS infrastructure in the state, benefiting the surveying profession in Georgia as well as eGPS Solutions.

"We believe that RTK GPS will be the next utility," says Sears, eGPS president. "We're giving away static files for free to advance and establish the network as the backbone of future adjustments in Georgia. It's a strategic move to promote the profession as well as establish ourselves in Georgia."

Firm Uses Less for More

The NGS CORS sites were a strong selling point for Wolverton and Associates Inc. (W&A, Duluth, Ga.), a full-service civil engineering and surveying firm that has been using the eGPS network since November 2004 primarily for project and photogrammetric control for various transportation and site projects.

"They're not only providing a network to users, but are also helping the entire surveying community by densifying the NGS CORS network," says Lewis Brown, RLS, W&A director of surveying. "We were pretty sparse with our reference stations in Georgia, so it benefits us all."

Since W&A currently provides surveying services throughout the state, they are able to use the network for about 50 percent of their projects. The network is advantageous in providing control and location of features for a variety of projects including boundary, as-built and topographic surveys, photogrammetric control and construction staking. "Our survey crews enjoy using the new technology-and saving time," Brown says.

"A major benefit [of the system] is [in] reducing the number [of survey monuments] and [the] effort in finding survey monuments," he says, indicating that the eGPS monuments already have control. "In the past, we could spend half of a day and as much as a few days finding adequate monumentation prior to eGPS. That's quite a bit of time savings."

In addition, if it makes sense for a particular project, the network has enabled W&A to use one-person crews. Rather than having someone "babysit the base," as Brown puts it, one-person "crews" can now do the work of two people. And saving labor-power is something several Georgia firms see as critical. Qualified surveyors are hard to find in the southern state; Brown is training his own-and eGPS founder Travis Pruitt Sr. lists limited surveying personnel as a major factor in the initial decision to implement the network.

"That's the reason we went with the network," says Pruitt, LS, PE. "We have not been able to hire enough people to do the work available to us. With the VRS network we have the potential of at least doubling our output." In fact, TP&A has been able to produce field surveys more quickly with more efficient use of their labor than was experienced prior to implementing the VRS system, he noted.

Ga.Kue Xiong and Chad Boggs of Travis Pruitt & Associates Inc. stake lot corners for pad grading in a residential subdivision in Cumming, Ga.

The Specifics of the System

The network technology reduces more than just time, labor and the need for a base station. On the management side, the Trimble (Sunnyvale, Calif.) VRS technology used in the eGPS system increases network range while limiting the number of reference stations required to cover a large area.

Because Trimble RTKNet software is able to process the entire network simultaneously, Trimble VRS networks offer greater quality control and higher data accuracy at longer distances. In the field, the farther users get from a reference station using conventional RTK, the more susceptible they become to reduced accuracy and performance due to systematic errors such as ionospheric and tropospheric effects. In a Trimble VRS network, RTKNet software provides a fully modeled solution that factors in potential systematic errors. Users connect into the system using a wireless connection; the software acknowledges the users' field positions and allows them to operate as though there is a reference station-a virtual reference station-right next to their rover. As a result, the PPM error is eliminated or significantly reduced, allowing surveyors to achieve RTK precision over much greater distances with fewer reference stations. Users can also retrieve stored GPS correction data from a control center via the Internet for post-processing.

The Trimble VRS solution enables GPS network administrators to provide RTK corrections through the Internet using industry standard (RTCM) protocols as well as supply built-in access, authentication and accounting of users. This allows network administrators as well as IT managers to control who is accessing their system and how often-and where they are in the field. Users then access RTK correction data in the field via a cell phone connected to a GPS rover. Because the VRS operates on Internet protocol, users don't need to be in radio broadcast range like they do with a conventional RTK radio transmitter.

Additionally, along with offering scalability in the number of reference stations, network configuration and architecture are also scalable. Trimble VRS networks can run on just one server-or have 10 or more servers running GPS solutions, depending on the redundancy, reliability and processing power required. The eGPS network runs on a dedicated server with backup for redundancy; eGPS plans to expand this as demand increases.

Charter Member Experience

Frontline Surveying & Mapping Inc. (Marietta, Ga.) President and CEO Thomas E. Peay Jr., RLS, not only signed on as charter member of eGPS, but also owns the network's Bartow County reference station. Peay had been interested in implementing a VRS network for a while, and offered eGPS a reference station to move the network forward. Frontline today has two licenses; in the future Peay hopes to increase the licenses to cover his seven survey crews.

The full-service engineering and surveying firm, which does mainly land development topos, is often required to base its surveys on county GIS monuments. Peay will frequently find errors of up to 1 ft in monument positioning. He now ties the monuments into the bluebooked eGPS network to "nail it very tight," he says.

"We list the local monuments in our software, set up control and use eGPS to stake out the nearest monument and double-check the accuracy," he says. "We want to get the eGPS value instead of the recorded value. The accuracy is much better."

At times, if a portion of a jobsite is cut off from cellular coverage, his crews will set a base on a hill to bring in control from the eGPS network, then perform the remaining survey with conventional RTK. If there are a lot of trees in the work area, the crew will locate control with eGPS and traverse it onto the site conventionally.

"Whatever portion of the job can be done by eGPS we'll do," Peay says.

Jonny Coe of Travis Pruitt & Associates Inc. stakes out a DTM on a mass graded commercial site in Buford, Ga.

Support Before and After

Along with the technology, eGPS offers a plethora of support and services to users. Prospective users get a free one-week trial period; Sears will personally train the user in a day, leave and come get the rover at the week's end.

"The trial period has convinced a lot of people that this is very powerful technology they can make money with," he says.

The eGPS president has quickly become an expert on the various cellular networks and systems in the area. Sears will personally escort new users to a cellular store and pick out the phone that best works with the RTK GPS network.

eGPS also holds monthly roundtable dinner meetings, often hosted by a subscriber, that provide training and discussion based on users' questions. Since the technology and network are still relatively new, the forums are well-attended, providing more of a co-op feel for network users, according to Sears. eGPS also consults with firms on the use of a VRS network.

For network user Jack Berry Jr. of Jack Berry & Associates (JB&A, Peachtree City, Ga.), eGPS measurements are "right on the money-every single time."

"The eGPS network is unbelievable," says Berry, vice president of the aerial mapping and topographic firm. "It speeds up my field time. If I have three jobs in the same county I can go out and do all three jobs in one day. Without the network I'd have to use another GPS receiver for a base and it would take me five days to run the same three jobs."

JB&A has been using GPS since 1988. Over the years, the firm has had at least six GPS base stations stolen. eGPS eliminates that problem. This year, JB&A invested in a Trimble 5800 GPS receiver and TSCe controller to use with the eGPS network. With productivity savings from the network, Berry estimates the rover paid for itself within three to four months. As long as the firm uses the network for one control project a month the subscription is paid for-"and the rest is profit," he says. "The difference in time and productivity between the network and our static sessions is amazing. We have enough work to keep us busy with the network, and our other crews can use our six other GPS receivers doing static sessions outside the network and in other states."

Growing eGPS

In the future, eGPS plans to extend the network to cover all interstate corridors and ultimately be statewide, according to Sears. "We're already covering a huge footprint," he says, "but in the future, anywhere there's cell phone coverage, we'll be there.

"I tell potential users they can expect as much as a 50 percent productivity increase using the network. I know it's more than that, but I'd rather under-promise and over-deliver. With photogrammetry you can see approximately 300 percent productivity increases while boundary topos gain around 20 percent-but everything in-between depends on who's running the survey and how motivated they are."

Lowe Engineers' partner in charge of surveying and mapping, Bill Daniel, LS, CP, is a strong supporter of the eGPS network-and similar networks across the nation.

"I think the need for RTK GPS networks are immediate," Daniel says. "States or areas that don't have them or aren't planning for them will be behind the eight-ball if they don't get them soon.

"We're already wanting the network to be everywhere we work," he said. "˜We're spoiled and we've only had it six months. I see the day coming when everyone will have access to a base station with centimeter-accuracy by dialing up and hooking into a network like this."