REMOTE SENSING
High-Resolution Imagery Aids Civil Engineers
Growth outlook strong in European markets

Space and airborne imaging systems have been with us for over 25 years, but only since the end of the Cold War have laws governing the availability of high resolution imagery been relaxed to allow almost unrestricted distribution of images with a 1m (meter) ground resolution.
     Recognizing the potential economic and social benefits associated with the application of such space-based information, the European Commission's Centre for Earth Observation Programme (CEO) initiated several studies focused on different markets for this new source of data.
     Smith System Engineering Limited, a firm of technical consultants based in Guildford, UK, and NPA Satellite Mapping Limited, Edenbridge, UK analyzed the use of satellite imagery in common civil engineering feasibility and design tasks. Among the benefits from EO data are 1) reduced data acquisition costs: newly acquired "high resolution" optical imagery of any region of the world will be sold on a per unit area basis. Although prices are indicative at present, the policy of each vendor is to price their products at the same rate or lower than aerial photography products of equivalent quality. Increasing competition among space imagery suppliers will also ensure that space imagery remains cost competitive; 2) improved cloud penetration: radar imagery can be used for some civil engineering tasks in regions where clouds prevent aerial photography and high resolution optical imagery from being used; 3) non-intrusive data collection: imagery can be obtained of many areas of the Earth where access to aircraft is restricted (e.g., close to airports, sensitive areas and sites controlled by non-cooperative parties); 4) reduced processing and integration costs: information from satellites can be processed to order (e.g., to a specific ground reference system) and delivered in user-specified hardcopy or digital formats; 5) reduced delivery time-particularly for imagery from overseas locations or where access is restricted.
     Some civil engineering companies already use existing satellite imagery data, for applications such as pipeline routing and in heavy construction projects. Such projects often require detailed information on land ownership in order to compensate landowners for right-of-way passage on their land. In addition, basic information on, for example, existing infrastructure may be required for optimal project siting.
     Many of the largest pipeline routing projects are conducted in developing countries where suitable mapping is often non-existent, classified, lacking the required information, or out-of-date. Even where relatively recent survey data is available it can become outdated within a few years as developing countries are often undergoing rapid urban expansion.
     In a recent pipeline routing project, KVR 1000 imagery was acquired within 20 working days from the day of order. Through integrating this data with the available survey information, planners and pipeline engineers were able to readily correct systematic mapping errors, including correcting inaccuracies established with previous survey datums; locate other errors and changes requiring ground verification; and extend the property boundary data to cover areas that had not previously been surveyed.
     Many of the same obstacles confront heavy construction projects such as road building or infrastructure development. The successful management of these projects requires the ability to plan and visualize the site or likely route and to compute "downstream" project costs, important elements of which are often the collection of detailed geotechnical data such as soil and borehole data.
     Currently, the most suitable source of satellite data for such projects is KVR imagery with its 2m ground resolution. In the very near future, this will be supplemented with 1m ground resolution data from commercial systems. These data can be supplied as hard copy at a scale appropriate to the project size (any scale up to 1:5,000), or as digital files. Similarly, the derived products can be printed as both clear film and opaque paper copies, or registered in GIS to the imagery.
     Given the expanded capabilities offered through the use of EO satellite data, geologists are finding it increasingly valuable to interpret EO data in conjunction with other available data such as existing geological maps and cross sections to construct geological maps. Stereoscopic data from the new commercial systems will enable production of DEMs accurate to 2m-3m. Satellite imagery can then be referenced to the DEM which enables geologists to extract quantified geological information (e.g., the orientation of rock formations and faults).

About the Author:
For more information please contact Paul Brucciani at pmbrucciani@smithsys. co.uk. For more information on the CEO programme, contact http://ewse.ceo.org

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