Author : Francis H. Moffitt
Publisher : Unknown
Page : 46 pages
File Size : 50,7 Mb
Release : 1953
Category : Aerial photography
ISBN : UCR:31210024973420
Analysis of Controlled Terrestrial Photographs Taken at Davenport, California for Wave Velocity Method of Depth Determination by Francis H. Moffitt Pdf
Wave photographs were taken from a ground position about 90 ft above the sea level with an F-56 aerial camaera using an 8 1/4-in. lens pointed essentially parrallel to the wave crests and roughly normal to a pier which extended outward from shore to a distance of about 2200 ft. An electrically driven timer reading directly to 0.1 sec, capable of being estimated to 0.01 sec, was located in the foreground of the field of view of the aerial camera. The exposure interval varied from about 2 sec to about 4 sec with the comera operated altogether manually. The photographs taken with the F-56 aerial camera were arranged in sequence according to time and wave groups. Three different methods for determining wave lengths and wave periods were used. Similar wave photographs were taken a second time. The most difficult of all measurements was identification of the position of wave crests on the photographs. The investigation indicated that waves of a suitable nature (long period, fairly regular waves) give satisfactorily bottom profiles out to depths as much as 30 ft. The reliability increased as the number of waves measured increased.
