An Interactive Map Visualizes Great Lakes Water Currents

by   |   October 5, 2012 4:00 pm   |   0 Comments

Great Lakes Map image 2 for story1 An Interactive Map Visualizes Great Lakes Water Currents

A snapshot from the NOAA visualization showing current flows in the Great Lakes. Oceanographers use data feeds to update the water flows four times each day.

Sometimes the best design idea is to borrow someone else’s.

The National Oceanic Atmospheric Administration did just that to illustrate Great Lakes currents.

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The visualization shows current flow and speed by drawing white lines across the blue background of the Great Lakes at six different speeds—on the day of this writing, the strong currents flowing across Lake Superior show clearly why the freighter Edmund Fitzgerald wanted to make Whitefish Bay by the Sault Ste. Marie Locks leading into Lake Huron before it sank in 1975.

The visualization can also be switched from surface currents to depth-averaged currents, which will show how pollution would be moved.

Developers at NOAA adapted code borrowed from the Wind Map visualization introduced in late March 2012 that depicts wind flow across the U.S. It’s also interactive—it lets you zoom into an area and scroll over it to find wind speed and direction. (“It’s beautiful to look at,” wrote Nathan Yau at FlowingData.com.) The Wind Map was developed by Martin Wattenberg and Fernanda Viegas, who created IBM’s Many Eyes visualization project and are now co-leaders of Google’s “Big Picture” data visualization project.

Collaboration and Code Sharing
In fact, there were two stages of borrowing to get to the Great Lakes map. An oceanographer named Rich Signell saw the Wind Map and got permission to use the code for a map of coastal currents in the U.S.

Signell then told a colleague. “He said ‘hey, look what I did’”, says David J. Schwab, an oceanographer at NOAA’s Great Lakes Environmental and Research Laboratory in Ann Arbor, Mich.  “And we looked at the Great Lakes and decided there was enough interest in Great Lakes currents, and we went ahead with it,” Schwab says. (His lab has not yet received formal permission to use the code, so it is piggy-backing on Signell’s permission to use it).

Signell had written a script in Python to pull data on coastal currents from NOAA’s databases. In the Great Lakes lab, a research scientist, Gregory A. Lang, tweaked the Python script to work with its databases on Great Lakes currents (among other things, it changes wind speed to current speed). Lang also made it dynamic, because the Great Lakes data updates every six hours.

Lang said it took him about three weeks, working occasionally on it, to make the modifications he needed. He tweaked the code to change the graphic’s legends, to plot depth average current versus surface current, and to do monthly averages.

The hardest part of creating the visualization was learning Python, a scripting language Lang said he didn’t know. The visualization has required no maintenance since it was posted in early July, before the annual Port Huron to Mackinac (July 14) and Chicago to Mackinac (July 21) sailing races. Schwab says it received about 5,000 views a day when it was first posted.

Lang has received emails from, among others, Tom Skilling, the weatherman at Chicago’s WGN, who wrote “How cool is this! It’s fascinating!”

Other prospective users are less sanguine. A charter fisherman told the Great Lakes Echo that “for what we do, day to day fishing, I don’t see an application for it,” adding that he intends to continue using a current probe that he tosses over the side of his boat. But another charter captain posted in the comments on the story “I think it will help” explain movements of fish.

Schwab says the lab had worked on other ways to represent the Great Lakes currents, using vector maps and pseudo colors. Vectors represent how forces move things. “But vector fields are notoriously hard to visualize,” he says. “That’s why we were impressed by this technology.”

Schwab says the Great Lakes lab had come close to visualizing how currents circulated in the Great Lakes, but the Wind Map folks “did it in a very elegant way, and a way you can display on the Web very easily. “

Schwab, who studied computer science in the 1960s, called the current map “the kind of thing that you dreamed about” back then. “Now the day has come. It’s kind of cool.”

Michael Fitzgerald, an editor at LatitudeNews.com, is based in the Boston area. Follow him on Twitter at @riparian.

 

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