nadir point


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nadir point

[′nā·dər ‚pȯint]
(optics)
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

nadir point

nadir pointclick for a larger image
i. The same as nadir
ii. As it relates to aerial photogrammetry, it is the point where a plumb line dropped from the front nodal point pierces the photograph. This point is vertically beneath the exposure station. In the illustration, it is point N. Also called a photo nadir and a photo plumb point.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved
References in periodicals archive ?
For any given location in the satellite's coverage area, increasing altitude will result in increased range loss but, conversely, increasing altitude will result in reduced scan loss to all locations in the coverage area with the singular exception of the nadir point. For those points on the outer perimeter of the coverage area, this reduced scan loss can dominate the increased range loss to that point, resulting in a lower overall transmission loss and improved performance.
A precise calculation of relief displacement depends on knowing the elevation and the location of the nadir point of the original air photo, and the location (radial distance from the photographic nadir) and elevation of a point of interest (for this problem, a point that is relatively high or low and far from the center).
Another assumption is that the elevation of the nadir point of the photo is the mean of all elevations on the sheet.