Regional Control Supplied by Photogrammetryby G. Carper Tewinkel, (F.ASCE), Technical Assistant to Chief; Photogrammetry Division, U.S. Coastal and Geodetic Survey, ESSA, Rockville, MD,
Serial Information: Journal of the Surveying and Mapping Division, 1971, Vol. 97, Issue 1, Pg. 13-25
Document Type: Journal Paper
Where second-order geodetic control has a spacing of 3 miles to 5 miles, the positions and elevations of a virtually unlimited number of premarked ground points within a control figure can be determined with a rms error of 0.15 ft horizontally and 0.25 ft vertically for a total cost of about $5,000 for an area of 25 sq miles. A block of 25 photographs is a practical unit taken from an altitude of 5,000 ft to 7,500 ft with a glass-plate camera and an overlap of 60% in both directions. Corrections are made for comparator errors, film deformation (if film is used), lens distortion and atmospheric refraction, and a rectangular geocentric coordinate system is applied to recognize the effect of earth curvature. The premarked ground points become recoverable supplemental control. Thereafter lower-altitude film photographs can be used for mapping in three dimensions with conventional plotting instruments without any further field surveys.
Subject Headings: Photogrammetry | Photography | Deformation (mechanics) | Curvature | Spacing | Errors (statistics) | Cameras | Distortion (structural) | Geodetic surveys
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