Sea test development of laser altimeter
By: E.C. Crittenden, Jr., G.W. Rodeback, E.A. Milne, and A.W. Cooper
Contributors: Rodeback, George Wayne; Milne, Edmund Alexander; Cooper, Alfred William; Naval Postgraduate School (U.S.). Dept. of Physics
Publisher: Naval Postgraduate School; Available from National Technical Information Service
Published: 1991
Place of publication: Monterey, Calif; Springfield, Va
Language: eng
Number of pages: 22
Subjects: Reflectance; Laser beams; Angle of arrival; Ocean surface; Laser altimeters
Other titles: NPS-PH-91-006.
Description: Low altitude (81 m.) narrow-beam laser reflectance measurements were made from the      nearly ocean-like water surface under the Golden Gate Bridge. For short wavelength      waterways superimposed on swell, the signal amplitude probability distribution showed      periods of zero return signal, even for vertical incidence, apparently due to tipping of the      average water surface. The nonzero signals show an antilog-normal probability      distribution, skewed toward higher signal than that provide by a normal (Gaussian)      distribution. With incidence angle displaced from the vertical, the distribution shape is      retained but with more frequent zero reflections. The decrease with angle of the average      signal, including the zeros, is well fitted with a Gram-Charlier distribution, as seen by      earlier observers using photographic techniques which masked these details of the      structure. For the simpler wave pattern due to a long sustained wind direction, the signal      amplitude probability distribution is log-normal with no zero signal periods, for this case,      the distribution shifts toward exponential at large angles from the vertical. For surface      states intermediate between the above two extremes the distribution is often normal.      The larger return signal resulting form the skew toward larger amplitudes from lognormal      are more favorable for disposable laser altimeters than previously believed. Also for an      altimeter which may be swinging from a parachute or balloon, the return at angles from      the vertical remains high. The presence of occasional zero return signal does degrade      the accuracy of altitude somewhat for a descending altimeter, but the signal available      assures performance at larger altitudes than previously expected.
Notes: Title from cover.

"NPS-PH-91-006."

"January 1991."

"Final report for period October 1988 - December 1990."

AD A233 824.

Includes bibliographical references (p. 20).

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