It's Wednesday morning and Sean McGinnis is holding a giant orange orb.

"Let's go walk the balloon," says the IT specialist from New Jersey's Office of GIS.

McGinnis is holding a spool of 1,000 feet of kite string. Dangling from the balloon is a small camera protected by a modified plastic juice bottle. In minutes, it's floating hundreds of feet in the air — an orange dot against a bright blue sky.

Every two seconds, it snaps a picture of Penn's Landing and the Delaware River waterfront below.

"It's so cool," says Dana Bauer, a co-organizer of the balloon mapping event and a freelance mapmaker.

Later today, the group of about 20 workshop participants will reel in the balloon, download the pictures from up above and stitch them together using mapping software. (Watch this space later today for links. Here's a Flickr set of some of the aerial photos taken from the balloon.)

"It's fun," Bauer says. "For a lot of people data collection seems like a really boring process. But this is not boring.

"It's really public, it's visible, it's a way to engage people. And everyone loves maps, right? So the images that we take will be transformed into a really beautiful map of the waterfront."

That map will be available for everyone to see. Bauer says today's balloon event is very much a part of the city's vibrant open data scene.

But she says it's also about something true of a lot of other Tech Week events: "Nerdy enthusiasm."

On Thursday night that enthusiasm — and large printouts of the waterfront maps made today — will be on display at a happy hour for people interested in spatial data.