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Title: Techniques to improve astronomic positioning in the field
Authors: Baldwin, Angel A.
Keywords: Astronomical geography
Publisher: U.S. Army Engineer Topographic Laboratories.
Engineer Research and Development Center (U.S.)
Series/Report no.: ETL ; 0400.
Description: Research note
Abstract: This paper deals with new methods and techniques for improving astronomic positioning in the field. Latitude and longitude are obtained by observing transit times of pairs of stars over a fixed vertical plane, independent of azimuth and zenith distances. A unique solution is derived for each pair. Higher accuracy in latitude can be obtained by observing transit times of star pairs over the prime vertical, where the parallactic angle reaches its maximum value. The vertical plane of observation can be fixed within 90 arc seconds with respect to the prime vertical without changes in the star's parallactic angle, and a function of it, the latitude, can then be computed. The star transit times over different vertical lines are thereby reduced to the central line or collimation plane, as a function of the parallactic angle. Higher accuracy in longitude can be achieved by observing the transit times of pairs of stars over a vertical plane fixed within 20 arc minutes with respect to the meridian plane. Each individual star pair will determine a solution. Since each pair does not depend on azimuth orientation, the star pairs can be chosen arbitrarily with respect to declination or zenith distance, and short periods of clear sky observations can be utilized. When several pairs are observed an adjustment can be carried out through the equations of conditions that allow one to detect errors in either the transit times or in the star's right ascensions.
Rights: Approved for public release; distribution is unlimited.
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