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By Ann B. Tihansky, Shawn V. Dadisman and Brendan Dwyer
Students wear polarized glasses to see images in 3-D at the Geowall exhibit during the USGS St. Petersburg Open House.
Exploring geoscience data can be fun, especially when you put on a pair of polarized glasses and 'see' what scientists see in 3-D.
And while it's fun to look at, there is some serious science beyond the cool graphics. The methods used to collect these kinds of data rely on all types of new technology. Such detailed information provides scientists with tools to understand complex processes and changes over time. For instance, detailed elevation maps aid emergency managers by giving them tools to predict flooding and identify areas vulnerable to storm surge from hurricanes. By comparing images of the same areas over time, scientists can calculate changes to coastal-wetland habitat or identify areas where changes might occur in the future, such as flooding due to sea-level rise.
Tracking changes in elevation is particularly important to marine biologists because habitat type differs with elevation and water depth. Seagrasses seldom grow in water deeper than about six feet, so animals that rely upon them – including fish, crabs, and manatees – need access to these areas. On the other hand, salt marshes and mangrove forests require elevations that are under water at high tide but are occasionally dry when tides are very low. Both habitats support juvenile fish and crabs as well as many types of birds.
Enhanced imagery techniques allow scientists to see more than a "Bird's Eye View." This image of the Tampa Bay region, created with the on-line tool Virtual Ocean, combines NASA and USGS Landsat imagery. A bathymetric dataset and transparency settings can be selected to allow the viewer to 'see' beneath the water surface in offshore regions.
A close-up oblique 3-D view of the main channel of Tampa Bay north of Egmont Key, created with Fledermaus software and viewed through Geowall.
A map shows the paths of tropical storms (black lines) that have crossed the Tampa Bay region from 1851 to 2008.
A 3-D image of Tampa Bay, created with Fledermaus software, shows both topographic (land elevation) and bathymetric (seafloor elevation) data in a combined data product known as a topobathy map. You can learn more about these data at: http://soundwaves.usgs.gov/2007/07/pubs.html.
These new tools give scientists the ability to show geospatial information on an Earth-surface basemap. For example, topographic- and bathymetric-elevation data (both above and below the sea surface) when displayed together produce images like the large one of Tampa Bay on the right. These three-dimensional images enable scientists to see what would otherwise be lines on a map or tables of numerical data. When the data can be displayed visually, it can aid in the interpretation of spatial relationships. This technology is helping shed light on a wide variety of Earth-science phenomena. Some viewing capabilities require specialized tools and technology. An interactive display of information can be produced with Geowall, a visualization tool that uses both commercial and open-source software with dual projectors to display data onto one large screen. A software program called Fledermaus assembles the 3-D data, which are viewed with polarized glasses. Tampa Bay residents will have an opportunity to experience Geowall during the annual U.S. Geological Survey (USGS) annual Open House in St. Petersburg, held every fall (http://coastal.er.usgs.gov/openhouse/). Visitors can 'fly' through the channels of Tampa Bay or 'dive' into the Earth's crust to visually inspect datasets showing earthquake focus locations along a deeply buried fault.
Other technology is easily accessible on a home computer. Beyond the familiar Google Earth, online tools are available at Microsoft's Bing Maps, NASA's World Wind, and the National Science Foundation-supported GeoMapApp and Virtual Ocean. The last two are two-dimensional and three-dimensional Earth-viewing applications developed by the Lamont-Doherty Earth Observatory of Columbia University that offer many new ways to combine different datasets and see information.
The types of images that can be created are limited only by the data available. Along with the illustrations on these pages, other datasets allow viewers to look at earthquake activity along the Mid-Atlantic Ridge, fly through the geology of the Grand Canyon, or compare satellite images of the globe in summer and winter.
Get a real "Planet Earth" perspective. These tools are available on-line at: http://www.geomapapp.org/, http://www.virtualocean.org/, http://www.geowall.org/, and http://www.ivs3d.com/products/fledermaus/.
Use of tradenames in the 'Better Than Bird's Eye View' article is for identification purposes only and does not constitute endorsement by the U.S.Geological Survey.