. Forensic Use of Aerial Photographs, Satellite Imagery, & Historical Records It is often crucial to know what, where, and when activities with possible environmental consequences happened on a property. Historical records, maps, and other supporting information, if they exist at all, are typically incomplete and prone to large time gaps that prevent reliable recreations of site history and activities; however, integrating these traditional information sources with a detailed interpretation of aerial photographs and satellite imagery often provides a more time-continuous and defensible record of site activity that more adequately supports legal arguments, the identification of potentially responsible parties at particular times in a site's history, and the identification and investigation of potential sources and locations of contaminants. Remote-sensing images and historical records such as Sanborn and topographic maps and city directories are time-discrete "snapshots" than can be used in an integrated, interpretive manner to develop supportable reconstructions of phenomena that continuously evolve over time, such as human activity, site history, and land use. To use imagery and historical records in this way, they must be interpreted rather than simply "read". Image "reading" is concerned primarily with simple object and feature identification, whereas "interpretation" is the process of identifying objects, features, and conditions and assessing their meaning and significance. Image interpretation is therefore considered both reading the lines . . . and reading between the lines. Forensic applications of images and records include: Reconstructing (establishing a time line for) site history and land use Reconstructing the history of specific activities and events posing potential environmental liabilities Focusing the application of investigation and remediation resources Evaluating soil, geologic, and hydrogeologic conditions for water-supply development In addition to the technical tasks of image interpretation and inference, presenting the findings in a clear, concise, and visually pleasing manner is a critical aspect of image forensics that requires specialized staff, equipment, and software. AVANT staff are skilled at image interpretation and at developing graphics and presentations, including materials for courtroom presentations and litigation support. AVANT's forensic use of historical remote-sensing images involves several steps: Image and Map Acquisition AVANT obtains aerial photographs, satellite images, historical mapping, and other supporting records from numerous public and private sources in a variety of formats (e.g., paper records, single-photo prints or stereo pairs, film positives, digital images, etc.). In a typical Phase I Environmental Site Assessment, only a few of the most common image and information sources are accessed; however, other less-common image sources exist that can yield more time-continuous coverage of a property. Image Processing AVANT enhances images using raster (pixel) imaging software to improve their visual appearance and resolution, which facilitates observing and measuring features and structures of interest. This step requires a high-quality scan of the image so that its scale, brightness, and contrast can be adjusted to assist in its interpretation. Individual images can also be prepared digitally or printed on transparent material and superimposed to study and/or illustrate changes over time. Image Interpretation Image interpretation is comprised of a broad range of activities, depending on the objectives of the study. It may involve stereoscopic inspection of images to evaluate soil, hydrologic, environmental, or cultural features; the use of time overlays; and imposing reference grids to facilitate measurements and the documentation of changes through time. In most cases, the interpretation is integrated with reviews of historical mapping, other supporting information, and the findings of a site visit to provide "ground truth" reference information. Communication and Reporting AVANT communicates the results of image interpretation in a variety of ways - with line overlays to emphasize pertinent features, in chronological order, as animated time-lapse re-enactments, with an imposed grid to serve as a reference for locating features and tracking changes over time, etc. Attorneys, judges, and juries usually gain a clearer understanding of conditions and events when they are visually portrayed rather than described verbally. Exhibits derived from imagery and historical records are supplemented as necessary with charts, graphs, and diagrams. Other Services for Lenders, Financial Firms, and Attorneys Phase I and II environmental site assessments Asbestos and lead-paint inspections .

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