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1967 black-and-white photography taken for the Parks Division - Oregon State Highway Department, project "OC-3" The project was flown at 1:6000 scale with a 6-inch focal length camera lens in 66 flightlines flown between June and October 1967. The photography was scanned in 2007, ortho-rectified in 2008 using Leica Photography Suite. |
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1967 black-and-white photography taken for the Parks Division - Oregon State Highway Department, project "OC-3" The project was flown at 1:6000 scale with a 6-inch focal length camera lens in 66 flightlines flown between June and October 1967. The photography was scanned in 2007, ortho-rectified in 2008 using Leica Photography Suite. |
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This dataset was developed by the Southwest Washington Coastal Erosion Study, Coastal Monitoring & Analysis Program, Washington State Department of Ecology, with funding by the United States Geological Survey. |
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32904.3437493832 |
| typeKeywords:
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["Data","Service","Image Service","ArcGIS Server"] |
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There is positional error inherent in the ortho-rectification of the photo (ranging from 3-15 meters, but usually about 3 meters)
GROUND POINT MEASUREMENT & TRIANGULATION : The collection of "Ground Control Points" (GCPs) refers to identifying certain features in each photo whose geographical coordinates can be provided. Each individual raw photo had an average of at least 3 GCPs and about 7 or more Tie Points. The GCPs were obtained using the 2005 reference orthophotos to determine the geographical coordinates of features (e.g., road intersections) that were visible in both the 2005 and 1967 photos. The same feature was then identified graphically in the un-registered 1967 photo. Often, when road intersections or houses were not available, natural features were used, such as large boulders on the beach arranged in a recognizable pattern. The entire suite of 1611 photos along the entire coastline of Oregon were broken up into 48 individual "blocks", and each one was GCP-measured and triangulated separately.
Triangulation refers to the very quick process of hitting the "Triangulate" button and finding out whether or not the Ground Control Points (GCPs) fit together like a puzzle in a mathematically robust way. There is a resultant "Total RMS" error that indicates how well the geometry of the GCPs "converged". Convergence values greater than 4 meters were chosen as a threshold to indicate a problem and that GCPs had to be re-measured. The maximum positioning error of a single GCP was 16.37 meters; that was in a block whose block-average error was 4.61 meters. The average "Total RMS error" throughout all 48 blocks was 2.96 meters, and the average "Maximum error" of each of the 48 blocks was 10.70 meters.
ORTHO-RECTIFICATION: After triangulation, the creation of ortho-photos is straightforward and simple. It creates a new photo from the original raw photo by applying the mathematically converged geometry to the old photo. The new, ortho-rectified photo has a geographical coordinate (Easting and Northing) associated with each pixel. Features outside the center of photo are affected by the radial distortion of the camera lens and by the elevation changes of the terrain. These two factors can cause a feature (e.g., a house) to be incorrectly moved inward or outward from the center of the photo. The ortho-rectification process incorporates the radial distortion parameters for the given camera lens as well as the terrain model (Digital Elevation Model) to correct for these factors and move the feature to its correct location in the photo. |
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| title:
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OC3_1967_LowRes |
| type:
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Image Service |
| url:
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https://gisprod01.oprd.oregon.gov:6443/arcgis/admin |
| tags:
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[""] |
| culture:
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en-US |
| name:
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OC3_1967_LowRes |
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| minScale:
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6.73880959987368E7 |
| spatialReference:
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NAD_1983_2011_Oregon_Statewide_Lambert_Ft_Intl |