The Marriage of GIS and Land Surveying August 30, 2008Posted by Bahadir Sahin in Calismalar (Studies), English.
Tags: geographical information systems, gis technologies, land surveying, Trimble Geomatics Office
Too often the GIS professional and the surveyor are at odds; a hoity-toity GIS guy looks askance at a muddy-booted surveyor who wants to pin him down on accuracy and boundary issues, and the surveyor gets exasperated with the GIS guy who’s defining more parcels in an afternoon than he’ll work on in a month, but who can’t be bothered to think about metadata concerning monumentation or record survey information. Perhaps some surveyors have the sinking feeling that they missed the boat when it comes to GIS, that a new technology catering to measurement and boundary experts should really have added more to the bottom line of land surveyors than seems to be the case.
But things are changing. As GIS matures, survey grade accuracy is becoming more important and the value of a reliable boundary layer is increasingly obvious. This creates opportunities for land surveying firms, and Flatirons, Inc. of Boulder, Colorado is a good example of a company taking advantage. Flatirons (named for the Flatirons, an iconic mountain range above the city of Boulder) does “Surveying, Engineering & Geomatics” (and yes, they do list surveying before engineering). GIS design and implementation is a big part of their business, so this is a company that has had to think a lot about how surveyors and GIS types can work together. “GIS professionals aren’t currently licensed,” says J.B. Guyton, a licensed surveyor and CEO of Flatirons, “and the original authorship of GIS documents is important to surveyors. Chad and the other young guys here are helping us bring together the facts on the ground with the relevant legalities, and creating GIS boundaries that can better withstand court challenges.” `Chad’ is Chad McFadden, a senior project manager at Flatirons, who adds, “We’re both talking about the same points, after all–if we can unify this, we’ll be bringing the good things about surveying into GIS.”
A recent project for the City of Wheat Ridge, Colorado gave Flatirons the opportunity to try something new: Gather GIS data at survey grade accuracy, in one pass. If things went well, Flatirons would be able to move ahead with projects involving boundary monumentation. As Guyton says, “We’re figuring out how to marry these two disciplines, ancient and modern.”
New Tech Makes Marriage Possible
Wheat Ridge was working on a critical component of their new GIS, the storm sewer layer. The existing system wasn’t working. “They had paper map books,” explains McFadden, “but they were more wrong than right. Most of the system information seemed to be in one guy’s head, and he was too busy to update map books. So, we started to work on solutions.”
Wheat Ridge was working in concert with Jefferson County 911 program and all of the county’s cities. This made Flatirons’ job easier, as the county had standardized on ESRI software, settled on layer schemes, and worked through datum issues. “We started by converting an old storm water map to GIS. There was no metadata, and it was very inaccurate. Some points had been sketched in, some maybe surveyed, and some came from design–and there was no way to tell which was which. And it was incomplete; when we checked a few, we’d pop lids and find runs that weren’t shown.”
Obviously, new fieldwork was needed, and since the project would basically be an “as-built with a GIS deliverable,” per McFadden, the work had to be to sub-centimeter horizontal accuracy. This was new territory. GIS fieldwork requires standardized collection of a great deal of data. Gathering techniques have to be efficient and, well, easy: with more than 2,500 intakes, manholes, and outflows in Wheat Ridge, all with multiple attributes, crews would have to move fast and there wouldn’t be time to reinvent the wheel every day. By contrast, getting to sub-centimeter typically requires a certain fastidiousness, and the kind of confidence that comes with checking and rechecking. Typically, getting both types of information would take two passes–could Flatirons be fast and fastidious?
Not everyone thought so. “We came up with a method to capture all the data in one pass, at the required accuracy, and that’s what we based our bid on. There were two other bidders who said our way wouldn’t work. But with some help from Trimble, we proved them wrong.”
The help from Trimble came in two forms: a Trimble® VRS NowTM Network RTK Service, and a custom file output from Trimble Geomatics Office (TGO) software, simplifying uploading of data into the ESRI GIS.
The VRS Now Service in Colorado is the first in the nation to feature low band radio, in addition to cellular telephony, as a way to establish links with reference stations. For Devin Kowbuz, another Project Manager at Flatirons, this was a decisive advantage. “In the city, packet data takes a back seat to voice,” he explains. “This can affect our ability to stay connected.” McFadden adds, “The low band is privately owned by Trimble, and it can’t be trumped; we weren’t tied to a cell phone company, or limited by their network. The low band is good everywhere VRS Now is accurate.” Since base stations didn’t have to be set up for RTK, crews could get right to work and about an hour and a half a day was saved, versus conventional RTK. “We bid the job knowing we had the advantage of VRS Now,” says McFadden, “To hop out of the truck, grab a rod, and be surveying? That’s impressive.”
Another issue was data output. As sold, the Trimble Geomatics Office didn’t quite meet project GIS data requirements. McFadden wanted a collection process that “forced crews to gather the data,” while limiting entries to a `data dictionary’ compatible with the GIS scheme. And since 2,500 nodes with multiple attributes (such as direction, invert, composition, and pipe size) generates a lot of data, he wanted a streamlined download procedure to save office time. “I talked to Trimble, and they sent a developer right to our office who wrote us a piece of custom code for TGO that allowed us to output a single table that integrated flawlessly into the GIS.” The code also enforced the desired data collection routine and automated the lengthy collection process making it, if not easy, at least routine.