Monthly Archives: February 2010

Feb 22, 2010

Solar Activity May Impact GPS Users

By Mary L. Johnson

A solar flare that occurred on February 12, 2010 may signal a return to high solar activity after several months of sustained low activity.  Intense solar flares can cause temporary disruptions in GPS signals due to the high levels of radiation they release into the Earth’s atmosphere. 

Solar activity generally occurs in eleven-year cycles, with the next peak expected by 2012.  Increased solar activity is particularly troublesome for the navigation devices many drivers reference in their vehicles.  GPS blackouts may last for a number of minutes during periods of peak solar activity and may occur several times each year.  In addition to GPS blackouts, the atmospheric charge can impact the amount of time it takes for a GPS signal to make it to a GPS receiver, which causes inaccurate readings.  Positioning may be off by as much as thirty feet during these periods, which will have the greatest impact on GPS survey equipment. 

For iPhone users that want to keep track of solar activity, NASA has helped implement a new app called “3D Sun” that allows users to access a live global view of the sun.  Data is provided in near real-time fashion by NASA’s STEREO mission, a pair of satellites that provide coverage of both sides of the sun simultaneously.  More information on the app is available at http://3dsun.org/.

A high resolution 2D image of the sun taken by NASA's STEREO mission. STEREO is monitoring solar activity that may interfere with GPS and other signals. (Public domain image courtesy of NASA.)

A high resolution 2D image of the sun taken by NASA's STEREO mission. STEREO is monitoring solar activity that may interfere with GPS and other signals. (Public domain image courtesy of NASA.)

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Feb 10, 2010

Current Exhibitions of Historic Maps

By Deb Boyer

We’re obviously pretty fond of digital maps and technology in general. However, sometimes you just have to marvel at the beautiful maps and images created by cartographers hundreds of years ago. With brushes, compasses, sextants, and not a computer in sight, they surveyed and recreated the physical world as they knew it.

Many of these historic maps have been photographed or digitized and are available online. In terms of maps of Philadelphia where Azavea is based, both the Hexamer and Locher maps on PhillyHistory.org and the maps available at the Greater Philadelphia GeoHistory Network give great insight into how the city has changed and developed.

There are some maps though that just have to be seen in person. This Spring, a number of museums and libraries are displaying beautiful historic maps as part of various exhibitions. If you have a chance, it just might be worth tearing yourself away from the computer for awhile to marvel at the talents of cartographers throughout the centuries.

The Matteo Ricci World Map (1602) at the Library of Congress: On exhibit for the first time in North America, this 5.5 feet tall by 12.5 feet wide map displays China at the center of the world and was also the first Chinese map to show the Americas. More information is available in the New York Times review of the exhibition.

Mapping New York’s Shoreline, 1609-2009 at the New York Public Library: An exhibition of maps, atlases, prints, and other items tells the story of New York’s waterways and harbors over the course of four centuries.

Mapping Discoveries in the Heavens and Controversies on Earth from the Harvard Map Collection: Maps are not always of land. This exhibition explores Galileo’s celestial observations and their impact on the world. 

Envisioning the World currently on view at the Princeton University Library: A traveling exhibition of rare world maps from the collection of Henry Wendt, a Princeton alumnus.

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Feb 02, 2010

Tombigbee, USA

By Dana Bauer

It’s tempting to take seriously Neil Freeman’s reimagining of the United States.

Philadelphia, Allegheny, Great Smoky, Lincoln, High Plains, Great Basin, Los Angeles…

Click to enlarge. Credit: Neil Freeman

Click to enlarge. Credit: Neil Freeman

Freeman, an artist and urban planner, reorganized the states into 50 bodies of equal population and presented this new political landscape on his website, FakeIsTheNewReal.org. He preserved major metropolitan areas and used dominant physical features — rivers, mostly — to name the new geographic units.

The resulting map is logical, thoughtful, and pretty damned faithful to the physical and cultural geography of our nation.

“It’s not serious,” says Freeman, “but people took it seriously.” (As in, you’ll split up Texas over my dead body.) Geographer Stentor Danielson, who blogs about environmental and social issues (with a spatial bent) at Debitage.net, suggests that the lumping together of South Jersey and Philadelphia rings true culturally but would be an environmental disaster. If it weren’t for the state border along the Delaware River, Philadelphia might have sucked the Pine Barrens dry.

“Really, this map is meant to be an ironic look at Electoral College reform,” says Freeman.

Freeman’s map caught a wave of attention when he first posted it to his website after the 2004 presidential election. Earlier this year it was picked up again by several political bloggers, including James Fallows and Matthew Yglesias. (Fallows invites his readers to imagine a decennial redistricting of the states to reflect changes in population: “In a reapportioned Senate each of of these units would have two votes.”)

Freeman followed a few simple rules:
1. Keep populations equal (Freeman’s states range from 5.4 to 5.6 million people, according to 2000 U.S. Census data. Actual state populations range from ~500 thousand to ~33 million)
2. Place major cities and close-in suburbs in a single state
3. When possible, follow existing state and county boundaries
4. Keep river valleys intact

“I used rivers as a guide for picking names,” he says. Turns out, this strategy makes a lot of sense. Freeman recently read ‘Names on the Land,’ an historical account of place-naming by George Stewart. “I think I was unconsciously following the names he gives in the book.”

Check out some of the Freeman’s other projects over at FakeIsTheNewReal, including my favorites:
Brooklyn Typology — linking photographs and data “to form a portrait of the urban fabric of Brooklyn”
Subways at Scale — aspatial maps of urban subways
Chicago Mile by Mile — photographing Chicago’s street grid

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