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The methodology of this project combines the dimensional accuracy of an orthographic drawing with the
efficiency, detail, color and realism of photography. Terrestrial
photogrammetric techniques are used to accurately combine a large
number of individual photographs into a photomosaic that is an
orthographic projection along the plane of the building fronts.
Photographs
are taken with Nikon® digital cameras in RAW format. The camera is
positioned to capture the curbstones, sidewalks and approximately 4 to
5 meters of a buildings height. The focal plane of the camera is
aligned parallel to that of the imaged area and a bubble level is used
to confirm that the camera is vertical. Scale variation is eliminated
by taking all photographs at the same distance from the building plane. A color card is used with each set of shots to ensure true color.
For
taller structures, the camera is raised vertically on a custom designed
and constructed fiberglass monopod that is fitted with a monitor and
leveling equipment. In order to minimize parallax displacement, all
photographs are overlapped by approximately 50%.
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Geomatic
techniques are used to accurately combine (rectify) the photographs. A
reflectorless total station surveying instrument is used to record
three dimensional points on the perimeter of the building facades as
well as other features such as doors and windows. CAD software is used
to create orthographic single line drawings from the points.
Photoshop® image-editing software is used to accurately combine the photographs. The survey drawings are used as backgrounds on which to digitally place the photos. The combination of precise image recording and geomatic rectification enables photomosaics to be created that are orthographic representations of the facades of the structures and that depict realistic detail and color. All objects on the surface of the plane of the building frontages are at the same scale.
It is possible to produce very high quality enlargements of each of the completed photomosaics that are over two meters in length.
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Jennifer F. Stephens - Photography and photomosaics
Arthur E. Stephens - Survey and rectification drawings
All images and web site © 2002-2007 Jennifer F. Stephens - except as noted
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