STP935: A Macrostereogrammetric Technique for Measuring Surface Erosion Losses on Stone

    Winkler, EM
    Professor, University of Notre Dame, Notre Dame, IN

    Pages: 9    Published: Jan 1986


    Abstract

    Vertical aerial photograph stereoscopic pairs are the principal resource for making topographic maps and terrain profiles. Based on the same principle, close-up stereophotographs were taken of a strongly weathered surface of Georgia marble. Profiles were drawn of the now roughened surface, and the surface reduction was measured against inclusions of unweathered hornblende. Overlapping close-up photographs were taken at a 1:1 size ratio with a Canon macrolens on a nonautomatic Canon AT camera mounted on a sturdy Velbon-Mini tripod. With the optical axis perpendicular to the stone surface, light was provided by both a ringflash mounted in front of the lens and reflected natural light. An ultrafine-grained black and white film (Kodak Technical Pan, TP 2415) was used, printed onto 12.7 by 17.8-cm (5 by 7-in.) contrast paper for a 5:1 enlargement of the original surface.

    A simple Abrams Heightfinder was attached to a small folding pocket stereoviewer with about two- to three-power magnification lenses. The accuracy of the optical height measurements was about ±0.1 mm, based on comparison with measurements employing a needle-point depth micrometer.

    The method described here is applied to the comparison of uncleaned with cleaned stone surfaces in terms of both surface shape and surface reduction.

    Keywords:

    masonry, masonry cleaning, stone surface macrostereogrammetry


    Paper ID: STP20020S

    Committee/Subcommittee: E06.24

    DOI: 10.1520/STP20020S


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