NASA's World Wind software lets you explore an unbelievable wealth of geospatial imagery, rendered in 3-D in real time.
World Wind is a newcomer to the world of GIS software. Similar in premise to the shiny but ultimately rather expensive Keyhole package (http://www.keyhole.com/), NASA's World Wind application allows you to explore a real-time 3-D rendering of planet Earth from orbit all the way down to ground level, using your keyboard and mouse to navigate. The package is available for freeas in both beer and speechand has access to over 20 terabytes of data, including Landsat and Terraserver imagery, USGS topo maps, and much more. World Wind loads and caches its data sets dynamically as you zoom in, so broadband and a fast graphics card are an absolute must!
3.4.1. Getting the Software
First off, go to http://learn.arc.nasa.gov/worldwind/ and grab a copy of the software. At 235 MB, it's a hefty download, but that constitutes the "starter set" of data needed by the application. Double-click on the .exe file, and it will install like any other Windows application. Make sure you pick a location on your hard drive that has plenty of space, because as you zoom around on the globe and use various features, you will begin to download and store a lot of data on your computer. If the application is installed correctly, you will be greeted with a nice Blue Marble-textured globe, as shown in Figure 3-11.
Figure 3-11. World Wind's startup view
3.4.2. Basic Navigation
Navigation is pretty simple. Hold down the left mouse button and move the mouse to rotate the globe. You can use the scroll wheel, or hold down the left and right mouse buttons together to zoom the scene. Holding down the right mouse button alone allows you to use the mouse to tilt the scene, and if there is elevation data for the area, you will be treated to a 3-D view like Figure 3-12. If you just click on the screen, it will center your view to that point. If you click on the "Key Chart" icon in the upper right corner, you can get a list of all the keyboard navigation options as well.
Figure 3-12. Mt. St. Helens, as rendered in World Wind
Once you zoom in to a certain altitude, you will see a NASA logo in the upper right corner and a red rectangle on the map. This icon lets you know that World Wind is requesting more data over the network, so be patient.
3.4.3. Exploring the Available Data Sets
World Wind has many data sets you can play with:
The textured globe you see when you start the application.
The default data set when you zoom in. The resolution of Landsat 7 is 15 meters per pixel. There are two varieties, normal and "pseudo," which is a false color map produced using the infrared bands in Landsat imagery.
Shuttle Radar Topography Mission (SRTM)
Digital elevation data for a given area. If you tilt the view by holding down the right mouse button and moving the mouse, you will be able to see mountains and valleys.
USGS/Terraserver 1 meter
The Terraserver images are the highest-detail maps World Wind can use at the moment. With these, you can see cars and swimming pools.
These are the traditional hand-drawn USGS contour maps of a given area.
These data sets are activated by the icons across the top of the application, as shown in Figure 3-11. They can also be manipulated by the Layer Manager, by going to Tools images/ent/U2192.GIF border=0> Layer Manager.
There are three specialty data sets that World Wind can use as well:
NASA's MODIS satellite data is used to provide markers that point out notable meteorological and geological events happing all over the globe: storms, fires, floods, and even volcanoes. If you click on the markers, you can get high-resolution images of the events at a point in time.
These are various animations of phenomena on Earth produced by the Goddard Space Flight Center. Everything from hurricanes in Florida to sandstorms in China to fires in Yellowstone.
The GLOBE data set is primarily composed of various statistics gathered from the surface of the earth: rainfall, temperature, humidity, etc.
All these specialty sets can be explored under the Tools menu.
World Wind also features over four million place names and boundary lines for countries and states, which you can view by selecting the "Borders and Places" icon on the toolbar. If you click on the big magnifying glass icon or go to Tools images/ent/U2192.GIF border=0> Place Finder, you will get a dialog box where you can type in a name to be taken directly to that location, as shown in Figure 3-13.
Figure 3-13. World Wind's Place Finder dialog
3.4.4. A Sneak Peek into the Past
Since World Wind is part of a NASA initiative to help educators, they are providing a peek at some future features of the program. If you click on the "Lewis and Clark" icon in the toolbar, World Wind will overlay the route Lewis and Clark took on their journeys, as shown in Figure 3-14. The numbered icons are interactive, and clicking on them will open a journal entry on the Lewis and Clark web site (http://www.lewis-clark.org/).
Figure 3-14. Lewis and Clark's journey, as shown in World Wind
Currently, there are no end-user tools to build the overlay files, but since this is an open source project, hopefully the tools will be forthcoming.
3.4.5. Final Thoughts
Until now, a desktop-mapping application of this magnitude would have been a pretty ambitious project, but it seems like NASA has pulled it off with World Wind. There is no SourceForge repository for it, but there is an active community in their forums, located at http://learn.arc.nasa.gov/worldwind/forums/. Thanks to Moore's Law, we now have the ability to play this data back on the hardware on our desktop. How far we have come from vellum and quill pens!