flight height to contour interval ratio—The ratio of height above the ground from which aerial photographs are taken to the contour interval of the topographic map photogrammetrically compiled from the photographs. The reciprocal of the contour interval to flight height ratio. If the flight height to contour interval ratio exceed the C-factor of the system, the contours should not be expected to fulfill the accuracy requirements.

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Source: NSPS “Definitions of Surveying and Related Terms“, used with permission.

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