January 5, 2013

Precision aerial photography the latest tool in planners', developers' kits

Orthoimagery uses scale photos to provide landscape and terrain details; Kennebec County environs now being imaged by project

By Betty Adams badams@centralmaine.com
Staff Writer

Orthoimagery gives a really close look at the face of the Earth and true distances between points.

click image to enlarge

Portland Head Light in Cape Elizabeth is depicted in orthoimagery from a flight in spring 2012. The three-inch resolution of the photo means each pixel of the image represents a 3-inch square. The Maine Geolibrary Orthoimagery Program is focusing on Kennebec and surrounding counties this year, as it hopes to update geophysical data that is a decade old. Counties and municipalities can buy into the program and get high-resolution imagery to help with planning and development.

Image courtesy of Maine Geolibrary Orthoimagery Program

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Information about the orthoimagrey project is available on the website of the Maine Geolibrary at www.maine.gov/geolib.

It shows striations in the rocks forming the breakwater around Portland Head Light and the shadows of the visitors walking on the lighthouse grounds. The same 3-inch resolution -- the best available -- shows individual rows of seats at Hadlock Field in Portland.

While the low-flying bird's-eye view fascinates, it can be even more important economically to transportation planners, utility districts, surveyors, foresters and developers.

That is the point being emphasized to counties and towns in central and coastal Maine by promoters of the Maine Geolibrary Orthoimagery Program, which is looking at updating images of the entire state, region by region.

The focus now is on Androscoggin, Kennebec, Knox, Lincoln, Sagadahoc counties. Last year it was on Cumberland and York counties, and almost all the larger cities bought in, as well as all the coastal communities, according to Joseph Young, mapping coordinator with the Department of Agriculture, Conservation and Forestry's Floodplain Management Program.

"Kennebec County is buying in, so all the towns in Kennebec get a 2-foot resolution image and they can individually upgrade to a higher resolution," said Robert Devlin, Kennebec County administrator. "By us participating, it significantly reduces the cost to the towns."

County commissioners got letters of support for the project from Augusta, China, Fayette, Gardiner, Vassalboro and Winslow, and inquiries from other municipalities. The sheriff and the county's emergency management director also supported the project.

"They said this would make a big difference in planning and response," Devlin said.

Devlin said he expected larger communities, as well as utility districts, to buy in.

The county is using $21,167 in capital improvement money to fund its share of the project.

"We felt it was something we could do to support the towns regionally and save them a significant amount of money," Devlin said. "It's replacing some geophysical imagery that's a decade old. Google Earth doesn't do high-resolution imagery in rural areas."

Fayette selectmen are holding a public hearing on their proposed purchase of 6-inch resolution imagery for $10,500. The hearing is scheduled to take place during the regular 7 p.m. meeting Monday at Starling Hall.

"The benefit is more specific boundary imagery accuracy," said Mark Robinson, Fayette's town manager. "Not only the town would benefit; so would individual property owners. It would assist in questions of boundary ownership, and for properties that border town boundaries, it would certainly benefit those landowners."

Fayette is bordered by Franklin County on the north and Androscoggin County on the west.

Robinson said it would give code enforcement officers a better degree of accuracy with regard to buildings in resource protection areas and building potential outside of those areas.

The Maine Geolibrary Orthoimagery Program calls for mapping the entire state in a counterclockwise circle beginning at the southern end.

"It's done by a plane flying at about 3,000 feet," Young said, although the altitude varies according to the resolution sought.

He refers to 3-meter resolution as coarse and something that can be taken from 10,000 feet.

"Portland purchased 3-inch imagery -- very high resolution, very accurate," Young said, and requiring a lower altitude. "Six-inch resolution gives a very clear resolution of decks and buildings, so when you're doing jobs as assessors or code enforcement officers, it helps both towns and the property owners."

The flight timing is climate-related. The images must be taken after all the snow melts but before the leaves come out, Young said.

The images are taken by Woolpert, an Ohio-based firm.

Young said all communities were notified about the project via e-mail and postcards, and a number of Kennebec County municipalities indicated their interest in participating.

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