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Value in Virtuality

Professional Surveyor Magazine – June 2006

Mary Jo Wagner

Ask any surveyor in southern Ontario who has adopted Cansel’s Can-Net GPS Reference Station Network about what is its most significant selling point and the answer will undoubtedly be the ability to achieve real-time kinematic (RTK) GPS accuracy without setting up their own base station.

To be sure, the advent of RTK GPS nearly a decade ago fundamentally changed the way surveyors could perform their positioning work; today it is still a mainstay for the majority of surveyors’ activities. However, with increasing workloads, surveyors have begun searching for advanced technologies that can take them farther, faster without sacrificing precision.

To be sure, the advent of RTK GPS nearly a decade ago fundamentally changed the way surveyors could perform their positioning work

Can-Net, created with Sunnyvale, California-based Trimble VRS (Virtual Reference Station) technology, seems poised to answer surveyors’ wishes.

“A significant benefit of Can-Net is that it works with no base station so there is no set up time or risk of theft,” says Kim Husted, land surveyor and owner of Kim Husted Surveying Ltd. (KHS) in Tillsonburg, Ontario. “Before, I could spend two days setting up the control and shooting a site, and someone would have to stay with the base station. With Can-Net, you just step out of the office and you’re working at plus/minus a few millimeters. It’s a great way to go.”

A Need for a Network

Based in Vancouver, British Columbia, Cansel is the largest distributor of land-based positioning systems in North America. As such the company has been only too aware of a rather predominant redundancy issue in the surveying industry. “With RTK GPS, we have a group of surveyors—particularly in densely populated regions—who all have their own high-end base station,” explains Stephen Fletcher, an Ontario Land Surveyor and Cansel’s national survey sales manager who managed Can-Net’s implementation. “It’s like everyone with a cell phone bringing their own cell phone tower with them so they can use their phone. If we could enable surveyors to use the same base station, they’d save themselves a lot of money and time.”

Cansel decided the time had come to implement VRS technology in a permanent reference station network in the Ontario area. The network offers surveyors a solution to cost-effectively increase accuracy and productivity in the field while removing the ionospheric and tropospheric-induced errors that typically affect traditional RTK GPS. The Can-Net VRS Reference Station Network takes the base station out of the base-rover equation and replaces it with a densely populated, permanent network of reference stations, faster and more reliable communication links, and Trimble’s RTKNet software, which creates a VRS network able to greatly reduce the PPM error.

Initially launched in September 2004 with nine Trimble NetRS stations, Can-Net has expanded across Canada to now include 32 installations. Thirteen of those installations are in southern Ontario and make up the VRS network. To date, Cansel has 40 Can-Net users, all of whom are either yearly subscribers or are renting Can-Net units from Cansel.

Requiring only a Can-Net subscription, rover, data collector and Web-enabled cell phone, users need only activate their receiver, connect to Can-Net’s IP address, and the network begins streaming RTK GPS data over the Internet immediately—a set-up time of less than “three minutes,” says Fletcher.

According to Fletcher, users can expect to achieve 1 cm horizontally and 2 cm vertically anywhere within the southern Ontario Can-Net VRS network.

Unlike traditional RTK where surveyors are subject to degrading accuracies the farther they move from the base station, the VRS solution’s RTKNet software utilizes a group of reference stations to factor in potential systematic errors and to model the local ionospheric activity. When users connect to the system, the software recognizes the users’ field position and sends a specific correction for that specific position, enabling them to work as though they have a “virtual” reference station next to their rover. With such a fully modeled solution, the PPM error is eliminated or significantly reduced, giving surveyors the ability to gain RTK precision at much greater distances. According to Fletcher, users can expect to achieve 1 cm horizontally and 2 cm vertically anywhere within the southern Ontario Can-Net VRS network.

Each Can-Net reference station is tied into the Canadian Federal Datum (NAD83 CSRS) and is independently checked using Canada’s Geodetic Survey PPP processing. That quality control, coupled with the rigorous quality-control modules provided in the software, assures surveyors that they can be “99.9 percent confident” that the accuracies achieved in the VRS solution are correct, says Michael Wolfe, Cansel’s GPS infrastructure engineer.

Improved accuracy is indeed a benefit of Can-Net, but Fletcher says its real attraction is increased productivity for less cost. “With Can-Net, users can put two crews to work for the same level of investment in base stations,” he explains. “Secondly, with traditional RTK GPS, you can waste the better part of the morning just setting up the base station and control. With this system you get to the job site, connect to Can-Net and you’re ready to work before you’ve finished putting the sugar in your coffee. That is a significant productivity enhancement, particularly for guys who are doing many small jobs.”

Small Jobs, Big Headaches

The chance to reduce time in the often time-consuming smaller jobs such as laying out houses was a significant draw for Husted.

A full-service land survey firm, KHS is a 20-year veteran provider of legal land surveys for property boundaries, lot grading plans, house layouts, and topographic surveys. An avid GPS and total station user, Husted says that while GPS enables his crews to work much faster at a higher degree of accuracy, base station set up time could slow them down. And that is particularly problematic for small job assignments.

“A base station is a big pain for small work,” says Husted. “When you lay out a house, for example, you can spend two hours just to set up a base line.”

Husted tested the Can-Net system for two-weeks last June to lay out a 20-mile long utility corridor—a project that would typically pose control challenges with conventional instruments. The Can-Net VRS solution allowed crews to perform the assignment quicker and with better accuracy—within 3-4 mm horizontally, says Husted. “That’s better in fact than the standard 1 cm that Trimble specifications state for a VRS solution,” he adds.

Although the RTKNet software behind the Can-Net VRS solution is a complex workhorse, Husted says the system is very user-friendly yet sophisticated enough for users to perform a multitude of calculations in the field.

Since becoming a Can-Net user, Husted is now using the system for “everything” including large topographic surveys, farm surveys, property boundaries and house layouts.

“Now when we do house layouts, by the time we would have messed around with a base station, we’ve already got the job done.”

“Can-Net works better than what we expected,” says Husted. “Now when we do house layouts, by the time we would have messed around with a base station, we’ve already got the job done. It has not only significantly increased our productivity and accuracy, it’s provided sizable cost savings in labor.”

Capital Outlay

For Gord McGuire, senior project manager of survey services for the City of Hamilton, Ontario, the move to Can-Net was all about dollars and sense. Common to municipal departments, McGuire faced daily budget reminders to produce more with less. That was compounded a few years ago when the City launched its aggressive capital revitalization program to rebuild its aging infrastructure, bringing a heavy workload to McGuire’s department and heightening the awareness that his current RTK GPS equipment would make it difficult for his team to meet the City’s goals.

Can-Net initially came to McGuire through the “backdoor” when he purchased the Trimble R8 GPS System; Cansel offered the Can-Net network as part of the hardware package. Since becoming a user in November 2005, however, McGuire says Can-Net has quickly moved to the front door of most of his department’s surveying operations.

“The ability to just drive to a site and turn on a cell phone is huge,” says McGuire. “We’ve already seen an increase in our productivity since using our new receiver with Can-Net.”

“The ability to just drive to a site and turn on a cell phone is huge,” says McGuire. “We’ve already seen an increase in our productivity since using our new receiver with Can-Net.”

One of the most notable rewards of the system came to McGuire’s department during initial testing last fall. Using only the Trimble R8, a cell phone, and the VRS network, McGuire and colleagues located and tied in 120 control points to create a full calibration set for the entire 1,200-sq-km city in three weeks – a control fabric that took years to complete with their former RTK system.

“The maximum distance we could ever get with our RTK system was about 5 km,” says McGuire. “Now we can go anywhere within city limits, hop out of the car, turn on the cell phone and the receiver and we have positioning anywhere in our city to engineering spec, which satisfies 99 percent of our positioning requirements. And I’ve saved $30,000 in equipment and about $13,000 in annual operating costs.”

It’s All in the Numbers

It is indeed difficult to argue the numbers, particularly when they relate to rising profits. That is exactly what land surveying firm Holstead and Redmond (H&R) has been experiencing since becoming a daily Can-Net user in August 2005. Based in London, Ontario H&R has been providing a variety of land-related services including topographic surveys, legal surveys, GIS and mapping, and utility layout for more than 50 years.

Patrick Levac, a land surveyor and owner of H&R, says the business case for Can-Net is simple—higher productivity, higher profits.

Patrick Levac, a land surveyor and owner of H&R, says the business case for Can-Net is simple—higher productivity, higher profits.

“My field crews can complete work faster because they do not have to set up a local base within the VRS network. We can turn the system on, connect to the network, and start working and tying in information within five minutes of arriving on site. With productivity higher, profits are higher.”

A Magic Stick

Clear line-of-sight is particularly important—in a total station application—when assignments take crews to busy construction sites where piles of dirt, materials, and machinery can quickly interrupt total station surveying activities. Steve Conway, field services manager with civil engineering company Gamsby Mannerow (G&M) in Guelph, Ontario has experienced this frustration many times on the job.

“The guys would often set up the total station—even a robot—and they’d lay out one side of the street and all of a sudden a dump truck would come and dump a pile of dirt in front of the station,” he recalls. “Then you would have to move it to do the other side of the street.”

G&M normally uses total stations, occasionally renting RTK GPS gear. However, as infrequent as the need to rent GPS equipment has been, Conway says the downtime in setting up, powering, and dealing with base stations on those occasions has pushed him to look for more efficient surveying methods.

After a two-week Can-Net trial last October, Conway signed on to the network, particularly because the Trimble GPS hardware and software is compatible with G&M’s Trimble 5600 Robotic Total Station System. Since acquiring the technology, Can-Net and its “magic stick” as Conway calls it, have become standard equipment at construction sites.

“With this VRS technology, Can-Net is allowing us to complete more jobs in one day than in the past because we don’t have to set up a base station and it eliminates our total station line-of-sight problems,” says Conway. “Recently our guys did a day-and-a-half’s worth of work in two-thirds of a day because they didn’t have to set up the total station in four different locations.

An additional benefit with Can-Net, says Conway, is that the permanent and continuous nature of the VRS system provides “perfect repeatable accuracy.”

Sold on the tangible benefits of the system, Conway says they are looking into expanding its application to other work, such as topographic surveys—a task they have traditionally performed with a conventional total station and GPS.

Quantifying Costs

Based on the success garnered by surveyors in southern Ontario, Cansel is focused on bringing that same achievement to other regions in Canada. A Trimble VRS installation went live in Edmonton in March and other installations are planned in Winnipeg, Calgary, Montreal, and other sites in Ontario.

Should Can-Net become a reality for these areas as well, more Canadian surveyors stand to learn the value in virtuality.

About the Author

Mary Jo Wagner is a Vancouver-based freelance writer with more than 10 years’ experience covering geospatial technology.