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Application of Photogrammetric Techniques to the Measurementof Historic PhotographsDavid A. Strausz19 March 2001Oregon State UniversityGEO 522 - Reconstructing Historic LandscapesProf. Ronald DoelTABLE OF CONTENTSINTRODUCTION .............................................................2REPHOTOGRAPHY AS A RECORD OF LANDSCAPE CHANGE .....................2TECHNIQUES ...............................................................6ANALYTICAL ORIENTATION SOLUTION .......................................9PROPOSED DEMONSTRATION ...............................................13APPLICATIONS .............................................................15CONCLUSION ..............................................................16APPENDIX A ...............................................................18APPENDIX B ...............................................................22REFERENCES ..............................................................27Strausz 2INTRODUCTIONThe science and art of photography has provided a record of past landscapes throughoutthe 150 years since its development. This record documents change due to the natural successionof vegetation, cultural development, environmental evolution, and other inexorable processes,both uniformitarian and catastrophic. The legacy of these images of past landscapes can be a richresource for the study of the processes and effects of change in the environment, at least forprocesses that operate in the time scale of hundreds of years. An effective tool to utilize thisresource is the technique of rephotography or repeat photography, in which historic photographsare recreated so that changes in the landscape that have occurred in the intervening time can bereadily detected and studied (Figs. 1, 2). This technique involves taking a new photograph as closely as possible from the samepoint in space, with the same camera axis orientation, as the original photograph. This can bechallenging when, as is often the case, the original camera position, and such parameters ascamera focal length, or even image format size, if the original negative is not available, are allunknown. Fortunately, much of this information can be derived directly from the geometricproperties of the image itself. In addition, it is not necessary for comparative purposes toreproduce the original focal length and image format size, since the same geometric propertieswill be inherent in any photograph taken from the same point in space and with the sameorientation. It is valuable also in the repeated photograph to recreate other environmental parametersof the original photograph, such as season of the year (important for vegetation comparisons)andtime of day (affecting shadow length and orientation) in order that the new image duplicates asmany original parameters as possible so that true change in the environment is more evident. This is not difficult to do once the spatial orientation of the photograph is established, althoughrecreating the precise time of day might involve considerable patience. Fortunately, theprovenance of much archival photography does record the date of exposure; further clues can bederived from the geometry of shadows in the image.There are many advantages in using historic photographs as evidence. The popularity ofphotography as a recording medium almost since its inception means there is an abundance ofimages taken for personal, commercial, and scientific purposes that have survived and areavailable for study. It is a remarkable landscape indeed that has not been recorded. A valuablecharacteristic of a photographic image is the immense amount of data that is recorded in theemulsion. At the moment of exposure a permanent record is made of the reflectance values ofevery object in the field of view. This record exists in great detail as microscopic chemicalchanges in the emulsion that can be resolved to at least 10 microns in the original image scale. The emulsions of even the earliest photographs have this level of resolution, which combinedwith the large formats common in earlier times, recorded incredibly fine detail. This detail canallow researchers to glean information from these images that was unrecognized by the originalphotographer.REPHOTOGRAPHY AS A RECORD OF LANDSCAPE CHANGERepeat photography over time has been recognized for over 100 years as a technique torecord and study landscape change. Sebastian Finsterwalder pioneered the application ofphotogrammetric techniques to the measurement of Alpine glaciers as early as 1889 (Hattersley-Smith). The sometimes rapidly changing morphology of glaciers has inspired many researchersStrausz 3to advocate the use of repeated photographs since then. G.K. Gilbert, in the 1899 Harrisonexpedition to Alaska, made photographs of glaciers with the specific purpose of recording scenesfor future comparison. He also repeated in 1903 a glacier photograph in the Sierras taken twentyyears earlier (Rogers, Malde, and Turner 37).There have since been many studies of landscape change utilizing repeat photography. Rogers, Malde, and Turner provide a bibliography of over a hundred pages of referencescollected during their own repeat photography research. Hart and Laycock have published anupdated (1996) annotated list of references of studies that have utilized repeat photography forthe study of vegetation change, cross referenced by area of study and type of vegetation. Several examples of these studies are Hastings and Turner, Rogers, and Sallach,documenting landscape change in different habitats of south east Arizona, the Central GreatBasin of Utah, and in New Mexico, respectively. These studies all utilized historic photographsgleaned from many sources, such as museums and archives, recreated the photos, and used themto deduce environmental changes occurring in the intervening years. In these studies, the onlyuse of quantitative measurement of change was by Sallach, who covered the photos with a grid tomeasure relative coverage of different vegetation types. Several studies have been made to assist in the management of landscapes byinvestigating the effects of potentially manageable influences, such as fire, disease, grazing, andother human interactions. Two examples are Skovlin and Thomas, and United StatesDepartment of Agriculture, which use repeat photography to document changes in the BlueMountains of Oregon and the Boise National Forest, respectively. The Blue Mountain studyrecognized


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