Surveyors plant brass disk to mark occasion, location

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LEWISTON — It’s a simple brass disk affixed to a buried, 4-foot-tall granite post.

It won’t be visible to passers-by; motorists won’t see it as they drive down Lincoln Street. It will be hidden from view for most people paddling down the Androscoggin River this spring and most pedestrians will really have to look to find it.

But it’s there, and the National Geodetic Survey knows it’s there, as of Saturday night. 

And that’s all that matters.

“It’s just a way for us to draw attention to surveyors and what what we do,” said Keith Morse of JKL Land Surveying, a member of the Androscoggin Chapter of the Maine Society of Land Surveyors.

The group bought and buried the new surveyors’ benchmark in Lewiston’s Gas and Light Park — the green area between Lincoln Street and the river, south of Locust Street. 

They erected a surveyors’ GPS over the mark Saturday and began taking readings.

Four hours later, they uploaded their data to the NGS and officially registered their new mark.

It was one of hundreds of marks being placed around the country Saturday in honor of National Surveyors Week, which begins Monday. It was one of three being placed in Maine. Surveyors placed new marks in Augusta and Portland, as well.

“The GPS you have, that’ll get you to within 50 feet of a point accurately,” said Kevin Cullenberg, an Auburn land surveyor. “This rig is accurate to the millimeter. It gets you down to the point of a pen.”

The NGS computer uses the data collected by Cullenberg’s professional rig over four hours to average and mark a precise, official location.

Unofficially, the new benchmark is located at 44 degrees, 5 minutes and 14.06 seconds north and 73 degrees, 12 minutes and 55.3 seconds west.

The new benchmarks won’t help automobile GPS systems find their way around, but it could help make the road they drive on a bit straighter.

Surveyors use the marks and their known, precise geographic coordinates to calibrate their equipment before they begin marking property lines, paths for new roads or trenches for utilities.

“If you are trying to build a pipeline to Montreal, you need accurate data,” Cullenberg said. “We can link to a GPS here electronically. Then you are able to link to other crews anywhere on that pipeline, and they’ll all be tied in to this one.”

The disks are everywhere, dotting the national landscape. Many can be found on mountaintops and historic buildings, placed decades ago. There are dozens in the Twin Cities, according to NGS, including on top of Mount David on the Bates College campus, in the northeastern abutment of the Lown Peace Bridge and on the railroad bridge that crosses Main Street north of Mollison Way.

“This is just a new one, that’s all,” Morse said. 

But it might actually be more useful. It’s just off the road, so it’s easy to get to and it has sweeping access to the sky, and thus, satellites. Better views of the sky mean quicker and more accurate readings for GPS units. That means better surveying.

“It all boils down to geometry,” Cullenberg said. “There are 32 satellites up there, and the government checks their positions twice daily so they know exactly where each one is. That’s why you can take something that’s floating around up there and get a precise location down here.”

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