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University of Nebraska–Lincoln

Welcome to Virtual Nebraska

About Virtual Nebraska

Virtual Nebraska emerged out of the Consortium for the Application of Space Data to Education (CASDE) project which began in September 1995 after Senator Bob Kerrey challenged personnel of the Jet Propulsion Laboratory (JPL) to find a better way to apply NASA's space data holdings to education. CASDE's primary objective is to utilize NASA's legacy of data, information, and technology to stimulate and challenge K-12 students to acquire and use scientific, mathematical, and other skills. Project partners are the University of Nebraska-Lincoln (UNL), JPL, and the University of Nebraska-Omaha (UNO).

Virtual Nebraska serves as the prototype state for one of CASDE's key objectives ~ Virtual America. It integrates CASDE data sets, imagery, tutorials, tools and information under one umbrella, thus serving as the mechanism that allows users to browse data without being preoccupied with the nuances of tools and esoteric data formats.

In general, Virtual Nebraska is an on-line archive of satellite imagery and aerial photography that gives users the opportunity to view the State's landscape from unique perspectives (e.g., at infrared or microwave wavelengths). Additionally, this web site offers digital elevation data, learning activities, image-processing tools, historical "looks" at over 600 cities, and examples of how remotely sensed data can be used to solve problems. We encourage you to use Virtual Nebraska to study the State's geography, learn about the history of your city, locate your school, monitor vegetation patterns throughout a growing season, or map the statewide distribution of snow cover in January.

Who should use Virtual Nebraska?

Although Virtual Nebraska grew out of an education project, use is encouraged by everyone. We have discovered that many people access this site simply to "see" what their city, county, or region looks like from above. Recognizing familiar locations, investigating "strange" shapes and colors, or identifying one's home or farm can be fun and challenging. So, take some time and "click around". We suspect that you will discover things you never knew about Nebraska.

It is also worth noting that data provided through this web site have been utilized by professional agencies, businesses and agricultural producers across Nebraska. Soon after the first version of Virtual Nebraska was published we began receiving requests for imagery and related data from engineers, architects, planners and others throughout the region.

How are the Data in Virtual Nebraska Prepared?

The data posted on this site were derived from a number of sources and sensor types. The amount of preparation involved is dependent upon a number of variables. Below are short descriptions of how the image data products were prepared for delivery over the web.

All Data

In order for Virtual Nebraska imagery to be delivered rapidly over the Internet, it is necessary to drastically lessen their size. Our challenge is to decrease image files of 20 - 180 MB down to 50 - 100 KB! The processes used to accomplish this task involved first, resizing the image (resampling), and then reducing the image detail through lossy data compression (JPEG). Once the image data have been resampled and compressed, they are moved into Virtual Nebraska on the web server. It should be noted that even though the images have been reduced in file size, in many cases, they remain relatively large (in terms of download time), especially if using a modem. After significant testing it was determined (in most cases) that imagery compressed to less than 50K, suffered too greatly in quality, and therefore, most files are larger than 50K.

Aerial Photographs

The imagery appearing in the Color-Infrared section of Virtual Nebraska is predominatly from the National Aerial Photography Program (NAPP). These data are cloud free and provide very high-resolution (lots of detail) views of the landscape. The majority of the images in this section are mosaics, meaning that two or more images have been electronically "stitched" together to comprise one single, seamless image.

The first step in getting these data onto the web is to scan (digitize) the photographs. All NAPP images in Virtual Nebraska are scanned at 300 dpi. Once the images are scanned, each individual frame/picture must be geometrically rectified. Simply put, this means the image is electronically "stretched and warped" to remove distortions, thus making the image "map-like" in terms of positional accuracy. Geometric rectification is necessary because raw digital images acquired from aircraft and satellite platforms contain distortions from earth curvature, relief displacement, sensor errors, as well as variation in sensor altitude and attitude.

After each image is geometrically rectified, an analyst must "stitch" all individual scenes together to make one large, or composite, image. One-by-one the images are pieced together until the mosaic is complete.

The final step to creating a mosaic is to "fine tune" the composite so that it appears as a seamless image with no breaks or edge-matching errors. In many cases, this process is the most difficult step of the three to accomplish. The difficulty stems from the fact that the individual images used to generate a composite may come from different times of the year, and in some cases, even different years. Consider the obstacles in trying to align a Spring and Fall image. A river that was overflowing its banks in the spring, will likely have receded and be much narrower in the fall. Likewise, a crop that was just emerging in April or May will appear significantly different in August, thus making it difficult to align adjoining images. Of course, there are methods that can be used to minimize certain errors associated with image composites; however, in some cases it is impossible to generate a perfect mosaic. Finally, after the mosaic is complete, the composite image is prepared for the Web (resampled/compressed), as described above.

Landsat-TM

The TM data available through Virtual Nebraska have been provided by the Multi-Resolution Land Characterization Consortium (MRLC), and subsequently processed as part of the Nebraska Gap Analysis Project. The steps involved in processing the TM data are similar to those of the aerial photographs described above. In this case, however, 18 individual Landsat-TM scenes spanning the 1991 through 1993 growing seasons were used. Once the mosaic was complete, a "cookie cutter" operation was used to define the state's boundaries. The resulting 1.3 GB image was then subset county by county, compressed, and then moved into Virtual Nebraska.

Historical Component

"Cross-curricular learning" is increasing in popularity in schools throughout the country. Teachers are beginning to search for new and innovative ways to make learning more interesting and applicable to "real life". Because remotely sensed imagery embodies such a wealth of information (from any number of disciplines) it fits naturally into multidisciplinary classroom activities. The imagery available through Virtual Nebraska can be thought of as the "magnet" that pulls the various disciplines together.

The historical component of Virtual Nebraska came to fruition soon after "core" teachers became interested in tying space imagery together with history. For example, there was interest in comparing old maps scribed by Lewis and Clark with current-day satellite imagery, trying to locate remnants of the Oregon and Mormon trials, such as wagon ruts, on aerial photography, and comparing archived photos of Fort Atkinson with current day images. The ability to click on a satellite image, or map, to access historic information and photographs was considered to be an excellent way for making the data more "real" and applicable to K-12 classrooms.

After briefly researching Nebraska history, we located the Nebraska . . . Our Towns, book series coordinated by Jane Graff of Seward, Nebraska. Following a brief meeting with Jane, it was determined that digitizing the books and making them available through Virtual Nebraska would be mutually benefiting. The end result is that users can now obtain historic information for over 600 Nebraska cities. No other state in the nation has such a comprehensive record of city history compiled under one source - it is truly one-of-a-kind. For more information on the creation of Nebraska...Our Towns

Are the Original Data Available via CD-ROM or FTP?

In most cases, the answer is yes. However, none of the original data available through Virtual Nebraska are pre-packaged and ready for delivery; (i.e., each request needs to be handled separately). For this reason, you will need to contact us directly to discuss your needs. In some cases a minimal fee may be charged to cover the cost of media and postage. For large requests an additional processing fee may be included. Please contact Milda Vaitkus at (402) 472-0306 / e-mail mvaitkus1@unl.edu to discuss your requests.

Can Posters be Ordered?

Our poster products have been very popular among teachers since the beginning of the project. They have proven to be very dynamic tools in the classroom. To order posters, contact Milda Vaitkus at (402) 472-0306 / e-mail mvaitkus1@unl.edu. You can preview some of the sample posters that we have available. Although only a few posters are shown, any image that is accessible through Virtual Nebraska can be made into a poster. All of the products are printed on a glossy photo paper using a high-quality HP DesignJet 755CM plotter. Due to the cost of the materials we must charge for the posters, however, only for the cost of production. Three sizes are offered: 36" x 48" / 24" x 32" / 18" x 24" at costs of $25 / $20 / $15, respectively.

Are Virtual Nebraska Workshops Offered?

Workshops are offered to educators and others interested in learning about remote sensing by CALMIT Through the NebraskaView program. Our workshops are flexible in that they can be specially tailored in length and content to fit the needs of individual groups. For instance, we have conducted /sponsored courses ranging in duration from 1/2 day to 5 days. We also will "take-the-show-on-the-road" to conduct the workshops off-site. In most cases the workshops are free. However, in some instances, registration fees may be collected to cover travel and lodging costs of the instructors. To find out more about These workshops contact Milda Vaitkus at (402) 472-0306 / email mvaitkus1@unl.edu

Current Activities

The goals of Virtual Nebraska- adding new components, unique datasets, tutorials and tools on a regular basis are being implemented at CALMIT and through the NebraskaView program. On the CALMIT and NebraskaView websites you will find a variety of imagery available for download and many links to other sources of data and training opportunities.