| Satellite Imagery in Land Development Applications
The next generation of remote sensing instruments is now available off-the-shelf
By Tom Delaney As remote sensing technology has evolved over the past two decades, the age-old cost/benefit equation of capturing images via satellite is changing-dramatically, and in many instances, decidedly for the better. One relatively recent phenomenon has been the debut of highly precise, yet compact satellite-based imaging equipment capable of yielding images of breathtaking clarity at a reasonable cost to the customer. The result is a wealth of potential new applications for industries that have traditionally relied on earthbound data gathering. Among the most intriguing are zoning and land-use surveys.
Thanks to older Earth-from-space programs such as Landsat, virtually the entirety of the Earth's landmass has been imaged on a continuing basis since 1972, with a resolution of approximately 30 meters. Such images have been useful over the years to land speculators seeking to identify potential development sites and acquire a broad overview of an area up to 35,000 kilometers square. Furthermore, since satellite-generated images are digital, their storage, transmission, and manipulation was both easy and cost-effective. However, the granularity of the images severely limited their use to broad-brush geological surveys for regional land use or zoning exercises.
Individuals or organizations seeking more detailed images could commission aerial photography, producing full-color pictures acquired from an altitude of just a few thousand feet. This traditional fly-over approach has proven invaluable to land-use professionals by delivering a wealth of visual information about areas of interest.
Now, the promise of similarly clear, detailed images of the ground from 680 kilometers up is becoming a reality. The Eastman Kodak Company has dramatically advanced the state of spaceborne imaging, introducing a sophisticated camera system that will deliver startlingly crisp pictures from satellites in Low Earth Orbit (LEO). Kodak engineers spent over 2 years developing a digital camera (now known as the Model 1000ª). Initial specs described a state-of-the-art camera system comprising a powerful telescope, precision imaging sensors, and advanced subsystem electronics. The Most Powerful Camera in the World
Now available in an "off-the-shelf" configuration, Kodak's Model 1000ª digital camera comprises a series of precision-crafted elements designed to be launched by a small rocket. Thus, size and weight were two constantly recurring motives throughout the development cycle. For successful launch and optimal orbit, the entire assembly needed to top out at no more than 300 pounds, a number that kept engineers constantly on the lookout for technologies that would deliver the biggest bang for the buck-or in this case, ounce. Ultimately, the team made extensive use of the latest technologies, as well as carefully selecting each component for light weight and durability. The final result: a 1m square remote sensing instrument package that weighs just 100 kilograms (220 lbs.).
Proving once again the adage that good things come in small packages, the Model 1000 is arguably the highest performance commercial camera in the world. First and foremost, the optical telescope assembly boasts the resolving power of a 10,000 millimeter focal length lens. The telescope's three curved mirrors enable the instrument to focus images onto the focal plane precisely, while two additional mirrors bounce the captured images across the width of the telescope, rather than down its length. As a result, the telescope's length was shortened from 10m to just 2m without any loss of image quality. In another engineering "first," a unique honeycomb core was created for the camera's largest mirror, with a lightweight, porous sheet sandwiched between ultra-thin plates of highly polished optical glass.
The camera simultaneously captures panchromatic and multispectral imagery, in which special filters separate the components of red, green, and blue light, as well as the near-infrared waves that bounce off of the Earth's geographic features. The input generated through hundreds of thousands of pixels is then processed by CCD sensor arrays into discrete electronic charges. These in turn are converted into digital values, just as music is digitized for recording onto a compact disc. Once captured as digital image files, the data is compressed to a fraction of its original size for either storage on board the satellite or real-time transmission to a ground station. A Burgeoning Commercial Market
The promise of fresh, affordable images with 1m resolution is generating interest among a wide range of industries, with perhaps the most immediate application in land use and resource management. While many in this profession are already familiar with remote sensing technology, the availability of clear, detailed images is promising to take the industry to a new level. The combination of 1m panchromatic images and 4m multispectral images will offer users a visual montage that will readily allow them to discern similar-looking features. And images displayed in the near-infrared band allow users to see details not discernible to the human eye.
This level of granularity sparks the interest of land use managers such as Kent Asher, GIS manager for Rafael County, Georgia. Asher has frequently relied on spaceborne imagery in determining compliance with local ordinances that strictly limit new construction in flood prone areas of the county. Using the "big-picture" images, Asher can look at wide areas both currently and over time, pinpointing changes in the wake of new construction. In high-growth areas such as his, Asher says the terrain is highly changeable; images don't stay current for very long. Furthermore, rainstorms can produce dramatic changes in riverbeds and wetlands, changes that might go unnoticed without detailed "before" and "after" images. Asher says that apart from the pressing issue of soil erosion, the terrain he maps is highly susceptible to silt pollution-the mass migration of sediment and particulate matter from outside the county. Armed with the more accessible, affordable images promised by the new technology, Asher will be able to document more accurately the effect and take appropriate action in concert with surrounding jurisdictions.
The service might prove to be equally valuable to property developers weighing the comparative merits of different approaches to a construction project. Water and sewer expansions pose an expensive and potentially problematic situation for land developers. Through detailed satellite images, developers would gain an invaluable tool for performing feasibility studies, speeding key decisions such as whether to cut through a hill or create an artificial valley in support of planned improvements. The images can also constitute a time-lapse series for urban planners and civil engineers, documenting new construction and highlighting changing traffic patterns, as well as pinpointing areas of potential soil erosion and deforestation. With the precision and detail of Model 1000 images, conservationists and land development organizations may at last be able to find common ground in their competing missions for land use. As they gain the ability to document conditions and verify assumptions more precisely, both parties will also gain a shared understanding of the terrain in question and perhaps avoid divisive and time-consuming conflicts farther down the road. About the author:
Tom Delaney is a business development executive for Eastman Kodak Company's Commercial & Government Systems Division, based in Rochester, New York. Back |
