Roadside markers help state map I-90/39 expansion

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Tuesday, January 24, 2012
What it is: Motorists might have noticed scores of curious white Xs that dot area roadways near Interstate 90/39 overpasses throughout Rock County.

Conspiracy theorists and rumormongers rest easy. They're not part of any elaborate police speed trap. And, no, they're not targets for the Air National Guard to drop bags of flour.

According to Rock County Public Works Director Ben Koopman, the 4-foot Xs are control points for aerial mapping the Wisconsin Department of Transportation has slated in preparation for the planned Interstate 90/39 expansion.

Koopman said in the coming months the state plans to have a consultant do airplane flyovers of areas along the Interstate. The planes will collect hundreds of photographs of areas, with each photo capturing an image of the landscape a few hundred feet wide.

Koopman said a consultant will then create a patchwork of all of the aerial photographs to assemble a map of the Interstate. But not all of the photographs will match in scale. Some might overlap or have a degree of distortion.

That's where the Xs come in.

The Xs, a few of which are located in the county at Interstate overpasses along Kennedy Road and County O, are set on roadways for visibility and to mark distances. They're coded with numbers painted next to them, and they can be seen clearly in the photographs, where they serve as reference pointsócoordinates to mark distance.

That will allow technicians to justify each photo to its proper size and prevent portions of the map from getting out of scale, Koopman said.

"They can optically shrink or stretch each one (photograph) to keep them in scale,"

he said.

The state likely won't start flyover photography until March or April because snow glare and the sun's low angle in winter months can interfere with aerial photography, Koopman said.

After the mapping work, the Xs likely won't serve any other purpose.

In the past, the state has used a system of road markings for authorities to measure vehicle speed. But the Xs don't have anything to do with that system, and they won't be used for traffic enforcement or traffic studies, Koopman said.

Last updated: 7:15 pm Thursday, December 13, 2012

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