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One of the strategic goals of the Federal Highway Administration (FHWA) is to "protect and enhance communities and the natural environment affected by transportation." Environmental protection is accomplished through Environmental Assessments and Environmental Impact Statements (EIS) that seek to prevent adverse environmental effects from taking place rather than mitigating problems caused by past activities or practices. EISs are conducted in the context of an overall decision-making process that is inexact and fluid. Despite the fact that EISs are conducted in accordance with Executive Orders, environmental laws, and regulations, the process is laced with subjective components, such as "significant impact," "best available data," and loosely defined accuracy requirements. Although the rationale for EISs is environmental protection, they are not in and of themselves regulatory. The cost to the environment is weighed against the benefits of the proposed project. EISs are simply a source of information on which to base informed decisions...
Download Technology Guide NCRSTE_TG001 (PDF 3.4 MB)
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Planning and environmental assessment are transportation priority areas with high payoff potential for remote sensing. Planning is based on knowledge about the current state with some prediction as to how the state will change in the future. For long-range transportation planning by Federal, State, or metropolitan planning organizations, the information requirements may be less stringent as the focus is on characterizing general trends. Predicting the future is more precise if it is based on the historical trend projected through the present. The outcome of this process is to obtain a metric on trends and to steer thinking and planning activities internal to the organization. The accuracy of the prediction depends on the analysis method employed. Generally, however, data used for planning purposes is not required to meet precise accuracy standards...
Download Technology Guide NCRSTE_TG006 (PDF 3.1 MB)
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There is a general perception among transportation engineers that is shared among many professionals that have utilized aerial photography that high resolution remote sensing images from space-based systems at less than 10 meters to submeter scale would enhance their ability to accomplish work-related tasks. Although the resolution of satellite imagery is not comparable to aerial photography, the fact that these images can be acquired repeatedly and in a timely manner is certainly deemed an advantage. Furthermore, the fact that the images are digital and multispectral in nature opens the possibility that the images can be manipulated mathematically and classified in a systematic and repeatable procedure. It is imperative that one has a clear idea as to what information they wish to extract from imagery so that these goals can be matched to the appropriate data set. Each image data set has its advantages and disadvantages. Classification of high resolution imagery is not as straightforward as more traditional classification with lower resolution imagery (30 m or more)...
Download Technology Guide NCRSTE_TG007 (PDF 1.8 MB)
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Environmental streamlining brings together the timely delivery of transportation projects with the protection and enhancement of the environment. It is generally assumed that greater efficiency in acquiring and analyzing data used in EIS preparation, and better data standards, would reduce EIS preparation time and possibly result in less controversy over the report's findings. Environmental or development planning requires geospatial information about the distribution of landscape features. Maps, and to some extent aerial photographs, are the traditional sources of this information. Remote sensing offers tremendous potential for planning purposes because it not only affords a picture of the current state, but unlike aerial photographs, multispectral data can be used to provide information classes, such as land cover and land use. Continuity in temporal classification of land cover and its extension to land use can play a significant role in preparation of a comprehensive development plan and are invaluable in the planning stage of road development projects. Data from the Landsat satellite program are invaluable sources of information for regional- and some local-scale planning. Landsat data at 30 m resolution is suitable for relatively general natural resource classes, such as softwood and hardwood forests, pasture, cropland, residential and industrial areas, water bodies, etc. The U.S. government has funded the Landsat program continually as part of an on-going mapping program and data are relatively very inexpensive...
Download Technology Guide NCRSTE_TG008 (PDF 2.0 MB)
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Classification of remote sensing imagery is a means of compressing much spectral data into more readily understandable and interpretable information. In so doing, much of the noise in data is eliminated resulting in a signal that is relatively course. Detecting landscape change via image classification is limited by the high degree of generalization intrinsic to classification systems that stems from a) conventional dependence on a limited number of spectral bands, b) aggregation of information inherent in statistical approaches to classification and c) dependence on a single sensing system with a fixed spatial scale. The combined effect is that change is not detected until gross changes have occurred that are discernable within the generalization framework...
Download Technology Guide NCRSTE_TG009 (PDF 1.5 MB)
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