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Aerial maps help cities excel at lay of the land

Cities like Bloomington have used them for routine business. Now they help with everything from planning to zone enforcement.

January 19, 2010 at 5:32PM
This aerial photo shows a Bush Lake beach shelter. The blue line is a property line; the black lines show elevation.
This aerial photo shows a Bush Lake beach shelter. The blue line is a property line; the black lines show elevation. (City of Bloomington/The Minnesota Star Tribune)

The aerial photo of the Bloomington home is so detailed that you can see the garden, gazebo and patio in the backyard. The roof was being repaired when the picture was shot, and the yard is edged with evergreens.

Stack computerized information on top of that digital photo and you learn that the backyard drops about two feet from property line to house. The sewer line enters the house from the street near the middle of the lot, by a big tree. You could find out where the nearest fire hydrant is, whether there has been a car-deer collision on the street, and whether the homeowner has taken out a building permit.

The Big Brother aspects of gathering such information may raise the hair on the neck of privacy advocates, but aerial surveys of cities and the information that can be layered on that photographic base are the bread and butter of today's city planners. They combine very detailed information with the big picture of what a building, lot or neighborhood really looks like.

"Without the image, the information doesn't make much sense," said Glen Markegard, senior planner with the city of Bloomington.

Last month, the Bloomington City Council approved completion of a $153,000 project to shoot and process high-resolution photos of the city and update accompanying data files. The pictures, taken from an airplane flying 2,000 feet above the ground, will soon go live to form a sort of visual template for planners, who can layer dozens of databases on top of that image to produce almost any kind of map they want.

Want to know where the wireless antennas for cell phone services are? It can be mapped. Are antennas on high ground or low, near where deer congregate, by water mains or Indian mounds? Plug in the right data and you'll answer the question.

Most communities in the Twin Cities as well as metro area counties use such aerial images. Some cities, such as Edina, use aerials shot by Hennepin County. Bloomington, which has done seven aerial surveys since 1957, wanted photos taken from closer range, so it contracted for its own survey.

"It's a tool planners use all the time, every day," said Lance Bernard, president of the American Planning Association of Minnesota. "We're trying to understand development patterns -- where natural habitats might be, demographics, housing patterns, for park planning. ... Better data makes for more sound planning decisions."

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Available to the public

Some cities, such as Edina, make aerial images available on their websites. Bloomington's database, which is used by many city departments, is available on computers at service desks so staffers can call up information when someone comes in wanting to expand a garage or build a new driveway.

The wedding of data, records and images allows city staff to avoid mistakes that have been made in the past, said Bob Hawbaker, Bloomington's manager of planning and economic development. He pointed to a case in the 1980s where the owner of a large lot asked to build a new garage. He got that permission. After construction had already begun, the city discovered that the city had a right-of-way on the lot and there was a water main under the property -- right under the new garage.

"The information then was so diffused and complex," Hawbaker said. "This simplifies it."

The technology is changing all the time. Rebecca Foster, Edina's Geographic Information Systems administrator, has worked in the field for a decade and said that at the start, photos were black-and-white and manipulating data meant typing in computer commands. Now the work is Web-based and color photos are so detailed that fire hydrants, street curb and gutter, and even cracks in pavement are visible.

Foster has combined photos with city data to map fire hydrants for the Edina Fire Department in a program that can be called up on laptops in fire trucks. She also created a wall map of the city's golf courses, identifying fairways so when someone calls 911 with a report of a heart attack on the fourth hole at Braemar Golf Course, fire personnel know exactly where to go.

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What about Big Brother?

Planners say they don't have time to idly scroll through records looking for zoning violations. But in Edina, Foster said, if property assessors suspect a homeowner has built an addition to a home without a permit, the city can compare photos shot years apart to determine when that addition was built.

Bloomington police have used aerial pictures to figure out how to unobtrusively approach a property where they need to serve a high-risk warrant.

But Foster, who services on a new state advisory council on geospatial information, was puzzled when asked about privacy concerns about such detailed photographic systems.

"I'm looking for streetlights or where driveways come out on streets ... not where cars are parked or where people are standing," she said.

Bernard agreed that privacy concerns haven't been much of an issue for planners. If there is controversy, he said, it focuses on heavily used websites such as Google Map's Street View, where users can type in an address and get a frontal photo of a home that most city planners have.

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"That's a huge issue in this new world of technology," Bernard said. "When have people gone too far? But I don't think it resonates much from the planning perspective."

Mary Jane Smetanka • 612-673-7380

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about the writer

about the writer

MARY JANE SMETANKA, Star Tribune

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