Tait Danielson Castillo's office wall is dominated by a laminated map covered in erasable marker that's about as long as he is tall. It's 16 years old, and finally on its way out now that a new digital mapping system is dramatically changing how the neighborhood organizer reaches out to area residents.

Danielson Castillo is using geographic information system (GIS) mapping to layer several sets of data on a computerized map of District 7, a collection of 5,500 households just north of University Avenue between N. Lexington Parkway and Interstate 35E in St. Paul.

The depth and breadth of the mapping project, completed last month, is unheard of on a community level in Minnesota.

"The way he's using it, I don't think it's common at all," said Jeff Matson, coordinator of the Community GIS Program at the Center for Urban and Regional Affairs at the University of Minnesota. "I've been waiting forever for someone to run with it like he has."

With the click of a mouse, Danielson Castillo can find the neighborhood's gardeners or crime hot spots. He can even identify every city-owned tree and tell you what type it is.

"It's helped us better connect to the neighborhood," said Danielson Castillo, executive director of the Frogtown Neighborhood Association. "The goal has always been to just more efficiently connect to the people who want to know information about their neighborhood. It's not necessarily about being Big Brother."

He can layer numerous sets of public data such as property lines, crime statistics, vacant lots and streetlights, with private information volunteered by homeowners. Residents can decide whether or not to provide their own data such as names, contact information, organizational affiliations and interests. Danielson Castillo said the information is not shared publicly.

Each set of data can be viewed on the map alone, or together in infinitely different combinations.

Danielson Castillo and his colleague, Sam Buffington, can select a topic such as "gardening" from a computer menu, and homes with people interested in gardening will change color on the map. They can then click on individual homes to pull up that person's name and contact information.

In October, they used the GIS map to identify which vacant city properties would attract the most community gardeners. Instead of randomly door-knocking to query interest among the district's 17,000 residents, the map was used to identify residents who already had expressed interest in the topic. Several lots closest to those residents were selected.

"In this case, technology has brought us back to the roots of community organizing," Danielson Castillo said. "If I can inform a group of 100 neighbors in a day about a concern or a problem or something positive, I can do that quickly and then go out and door-knock to make sure they participate."

Most of the information is public and obtained from the city. The computer software integrates it into the map in a matter of minutes. Some information is hand-gathered, such as alley light posts, which have to be purchased privately by homeowners in St. Paul. They're sporadically located and sometimes rare in low-income areas.

Danielson Castillo is in the middle of an ambitious project to map every alley light post. He has to drive down each alley in District 7 armed with a handheld GPS device that looks like a cellphone on steroids, park under each light and plot it on the device's map. The device shares that information with the GIS map.

His question: Do alley light locations affect crime patterns?

Every city-owned tree in the district shows up on the map as a green dot. Click on a dot, and a small window pops up on the computer screen identifying the type of tree. The goal? Keep track of trees vulnerable to disease (such as emerald ash borer or Dutch elm disease) and how that might affect homeowners' trees that could fall prey.

"It's got amazing potential," Matson said. "It gives them one more way to see the work that they're doing in a complete context."

Earlier this month, Danielson Castillo used the map to notify residents on Thomas Avenue who would be affected by sewer work that would interrupt their water service. A city contractor had been notifying residents with fliers, but Danielson Castillo said his warning was person-to-person and days in advance of the fliers, which residents often ignore as junk advertising.

In October, he used the map to find and call residents in a specific neighborhood about a rash of burglaries instead of using a general e-mail blast that might not have reached residents who needed it most.

Danielson Castillo said information also will be used proactively. For example, residents will be alerted when grants and programs for home improvement projects become available.

The project was funded with a $20,000 grant from the McKnight Foundation, but Danielson Castillo and Matson believe it's a tool that will become increasingly common and affordable for community organizations. Danielson Castillo already has given demonstrations of his GIS map to a number of community organizers, including Peter Fleck, a board member of the Seward Neighborhood Group in Minneapolis.

"I think Tait's tool is practical for any neighborhood, with a bit of training," Fleck said. "Now that he has a system in place, it can be shared with other neighborhoods or possibly sold."

Chao Xiong • 612-270-4708 Twitter: @ChaoStrib