SAN FRANCISCO — Mapping technology giant ESRI has created a new Web-based tool to provide access to 30 years of global Landsat satellite imagery and enable users to identify changes in specific regions over time. Users can see a vivid depiction, for example, of Alaskan glaciers melting, the forests of South America being converted to farmland and the explosive growth of urban areas from Dubai, United Arab Emirates, to Las Vegas.

The first iteration of the new website, ChangeMatters, was unveiled May 3 at a meeting of the American Society for Photogrammetry and Remote Sensing in Milwaukee. Company officials already are preparing plans to enhance the site, said Lawrie Jordan, imagery director for ESRI of Redlands, Calif. A new version, scheduled to be released sometime in the next three months, will offer improvements in imagery color and allow users to download data, Jordan said in a May 16 interview. The site also will be updated with 2010 Landsat data as soon as those data are available, he added.

ESRI developed ChangeMatters to give people who are unfamiliar with geographic information services and remote sensing a simple way to use imagery acquired between 1975 and 2005 by the Global Land Survey Landsat satellite missions, which are jointly managed by NASA and the U.S. Geological Survey (USGS). The ChangeMatters website allows users to view Landsat’s moderate resolution, 30-meter imagery against the backdrop of aerial photos, local topographical maps or street maps.

Users also can compare side-by-side images of a specific area taken decades apart to see the changes that are apparent in infrared imagery or in the visible portion of the electromagnetic spectrum. Someone interested in flooding in the Mississippi River basin, for example, could zoom in on that region and click on a box marked “Land/Water Boundary” to view the images with the Landsat spectral bands used to identify water.

“Landsat imagery goes back to the early 1970s and is essentially a continuous picture of the surface of the entire Earth,” Jordan said. “You are able to go back in time and see pretty dramatic changes in land cover.”

In 2008, the U.S. government began making all data acquired by Landsat satellites available to the public online at no charge. “Landsat satellite imagery is one of the most valuable resources for Earth observation,” David Hayes, U.S. deputy interior secretary, said in a May 3 statement. “ESRI’s Web site achieves the kind of thing we had hoped to see happen by making USGS’s Landsat dataset available to the public. The website will enable people around the world to more quickly and easily see how landscapes have changed over the years.”

By providing people with a visual tool to identify the impact human activity is having on the planet, ChangeMatters is also a political and environmental tool, said Kass Green, president of Kass Green & Associates of Berkeley, Calif., a firm that worked with ESRI to design the ChangeMatters website and change detection software. “ChangeMatters gives anyone in the world the ability to see change over time,” Green said in a May 18 interview. While the Landsat data were offered online previously, it was difficult for people to gain access to the data and there was no software available to make it easy for people to use the data to spot changes in the landscape of a specific area, she said.

ESRI provides access to the massive collection of Landsat data, approximately eight terabytes of information, by putting that information on the company’s cloud-based network. While offering a useful, free tool for viewing Landsat data, the ChangeMatters project also is giving ESRI officials the opportunity to test its cloud-based computing architecture as well as the ability of its software to create online mosaics of the various Landsat scenes. Through ChangeMatters, the scenes from 30,000 to 40,000 Landsat images are electronically stitched together to create whatever image the viewer is seeking.

The next challenge for ESRI will be to use the same model to offer customers online access to high-resolution satellite imagery through its ArcGIS mapping software. ESRI announced plans in April to license high-resolution imagery captured by Dulles, Va.-based GeoEye Inc.’s Ikonos satellite. ESRI plans to offer that Ikonos imagery through its ArcGIS website, Jordan said. That project is scheduled to be completed in 2012.

GeoEye of Dulles, Va., launched its Ikonos satellite in 1999. The Ikonos satellite captures black-and-white imagery with 82-centimeter resolution and multispectral imagery with 4-meter resolution.

In 2010, ESRI President Jack Dangermond conceived of the idea of using the company’s widely used ArcGIS mapping tool to offer access to Landsat data. ArcGIS already offered online access to a variety of maps and Earth observation data drawn from aerial and satellite sensors. Landsat data seemed like a natural extension of the product, Jordan said.

Debra Werner is a correspondent for SpaceNews based in San Francisco. Debra earned a bachelor’s degree in communications from the University of California, Berkeley, and a master’s degree in Journalism from Northwestern University. She...