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Remote Sensing

Remote sensing serves an essential role in creating a surface for Digital Earth

Three-dimensional virtual globes are successfully using realistic Earth-surface skins from remote sensing data to create intuitive and user-friendly graphic interfaces for nontechnical public consumers.
21 March 2007, SPIE Newsroom. DOI: 10.1117/2.1200702.0628

Remote sensing has long been the domain of rocket scientists and trained specialists. While satellite imagery has appeared in magazines and news reports, the public at large has been excluded from practical applications. This situation has changed with online navigation systems, such as MapQuest and Google Map, where a satellite or aerial photograph can be selected to serve as background for geographic searches for address locations. Increasingly, 3D mapping and geographic search programs, as exemplified by Google (Google Earth) and Microsoft (Virtual Earth), rely on vast quantities of remote sensing data to project an up-to-date and scale-satisfying experience for their customers. The expanded use of these Digital Earth geobrowsers offers an increasing market for improving the awareness and use of remotely sensed data by vast numbers of citizens as well as potentially raising the market volume of sales by the major geobrowser organizations. This trend may signal a forthcoming increase in the need for high-resolution data, as well as the development of special products for thermal, vegetative, and pollution-oriented delineations by nonvisible spectrum sensors.1

One of the more naïve and laughable laments of remote sensing stalwarts in the past was that remote sensing data had to be analyzed and handled only by trained remote sensing specialists. Their arguments held that without proper advanced training, people would misinterpret and therefore misuse the data. Many of my professional remote sensing colleagues would agree that it does requires training to understand the range of spectrum, radiometric, and other scientific-sounding parameters and their compounding influences on an expert's interpretation or analysis. However, when we apply photograph-like images of the Earth to geobrowsers, we observe little or no need for training. What you see is what you get: a view of the Earth that gets increasingly larger as you zoom into the cities or regions of interest. This is in exact harmony with the Digital Earth Vision, as articulated by former Vice President Al Gore in his 1998 speech on this subject.2 So at one end of the spectrum, we can see that no training is required for the public to quickly adopt and understand what they are seeing on the geographic search browsers. At the other end of the spectrum lies ample opportunity, albeit with challenges, to bring sophisticated remotely sensed data for increasing surface thermal trends, change detection, or other analytics to segments of this burgeoning public user community.3 These more sophisticated types of processed data will require some explanation to be more effectively consumed by the lay public.

The Digital Earth Vision that inspired the US Government's Digital Earth Initiative in 1999 proposed a future where a young girl would use a 3D virtual Earth to access digital information streaming from the network of the world's libraries, along with a host of other interconnected and interoperable data and information resources. This young girl would experience a profound transition during her learning experiences as she both researched and was entertained by vast amounts of material on art, science, history, engineering, music, and so forth, all at her fingertips. As government agencies, universities, nongovernmental organizations, and groups of businesses continued to collaborate and work on creating the components for the Digital Earth vision,4 the role of remote sensing appeared to resolve itself when most groups simply defaulted to the use of NASA's Blue Marble composite image of the Earth. The Blue Marble image, although undergoing many version updates, became the de facto reference data set for the geobrowser community, including such leaders as World Wind, GeoFusion, Skyline, Microsoft, Google, and others.

High-resolution imagery from commercial satellite data, however, has rapidly become the imagery of choice, as citizens become accustomed to seeing cars parked by houses that they can recognize as their own. A seemingly insatiable appetite has grown for the use of these imagery data, boosting the sales for commercial satellite images but also increasing the need for current imagery. Citizens are beginning to recognize that satellite imagery becomes outdated after a year or so, especially in fast-growing regions of urban sprawl or rapid deforestation. And it is in these areas of interest to the larger public that the remote sensing community may find increasing use for more sophisticated analytical products of their trade. Time lapse imagery and scientific detection algorithms may find a receptive audience interested in the location of hazardous legacy items near their neighborhoods. The US Environmental Protection Agency's remote sensing office in Las Vegas aggressively used satellite and aerial photography throughout the 1980s to effectively define hazards and illegal activities ranging from Superfund sites to wetland destruction violations. These same data and techniques could prove valuable to the public at large in a democracy where every citizen should have access to information about the health of the immediate environment.5 Remote sensing experts will need to supply this information.

For more information on the Digital Earth community and its history, visit http://www.isde5.org.

Tim Foresman
International Center for Remote Sensing Education
Baltimore, MD

Tim Foresman is president of the International Center for Remote Sensing Education. He was formerly the national program manager for NASA's Digital Earth Initiative, and chief scientist for the United Nations Environment Programme as director of Early Warning and Assessment.