GOVERNMENT TECHNOLOGY/Space-age imagery
Since the late 1990s, commercial high-resolution satellite imagery has been used extensively by numerous federal and state government agencies to support geographic information systems (GIS). However, the largest segment of government in the United States — cities and counties — has been slower to employ the imagery.
That is beginning to change, according to Tom Sweet, who, as chief operations officer for the Pennsylvania GIS Consortium, has been studying the use of satellite imagery in cities and counties throughout Pennsylvania. “Cities and counties are now beginning to realize how satellite imagery can help them stay a step ahead, save money and even provide the baseline for strong economic development,” he says.
Many local government organizations have used aerial imagery to create and update their GIS landbase data sets. Many choose that type of imagery because it is a mature, easily understood technology; the original film images have high resolution; and the images can be used to develop high-resolution digital orthophotography.
Nonetheless, traditional aerial photography presents many challenges. Namely, when the original film is scanned to create a digital version, resolution can be lost. Additionally, aircraft typically only capture images using a single type of film (i.e., panchromatic, color, infrared) per flight, so multiple flights over the same area might be required to obtain different images.
Because satellite imagery is obtained by a digital camera, it does not have the same limitations of traditional film-based aerial photography. For example, satellite imagery does not have to be scanned to create a digital orthophoto, and the satellite can capture panchromatic, color and infrared images of a large ground area simultaneously.
High-resolution satellite imagery has a few drawbacks, however. For example, the highest resolution orthophotos that satellites currently can generate have two-foot pixels. In the center-city areas of many larger cities, one-foot resolution may be desirable for certain infrastructure management tasks, such as identifying catch basins and manholes, that can only be viewed at that level of detail.
Taking the technology’s benefits and drawbacks into consideration, recent research, such as that done by Sweet in Pennsylvania, suggests that satellite imagery is well suited for tasks such as parcel mapping and property appraisal, emergency services management, development of GIS base maps, monitoring environmental change and fire prevention.
Local governments using satellite imagery can be perceived as business friendly by being able to provide easy-to-understand information about the condition of local facilities; type, size and location of land available for development; and tax structure. Satellite imagery provides that information for economic development and growth planning.
Because high-resolution commercial satellites are in continual orbit, local governments can obtain satellite imagery quickly to keep orthophoto landbase data sets up to date. With the availability of competitively priced two-foot pixel, high-resolution satellite imagery, local governments now have another option available to fulfill their digital orthophoto imagery requirements.
The author is president and CEO for Reddick, Fla.-based Emap International.
