ACCURACY OF HYDROGRAPHIC SURVEYING IN AND NEAR THE SURF ZONE
CORPS OF ENGINEERS WASHINGTON DC BEACH EROSION BOARD
Pagination or Media Count:
A statistical study was made of the accuracy that can be expected in hydrographic survey work where comparability of successive surveys is important. Tests were made at Mission Beach, Calif., to determine the magnitude of sounding and spacing errors. Sounding errors result from errors inherent in the sounder and the methods involved in reducing sounder data to an actual bottom profile to determine such errors, soundings were taken of a single profile 8 times successively in a 5-hr period. Echo-sounder data and leadline soundings were analyzed separately. For any one profile obtained by the echo sounder, an uncompensated error averaging 0.07 ft was indicated. With the leadline, a comparison of profile deviation against the average profile showed an uncompensated probable error of 0.11 ft comparison of successive profiles showed an error of 0.20 ft. A survey of more than 1 profile indicated that the surveying errors may be significant if toc few profile lines are used. Spacing errors result because a particular profile may not represent entirely its assigned section of beach. To determine spacing error, data were taken from soundings of sections of 1 11 ranges spaced 200 ft apart at 1-wk intervals and 2 47 ranges spaced 200 ft apart at 3-mo intervals. The portions of the probable error curves for spacings between 10,000-ft-long beach an error of 40, 000 cu yd can be expected in cubage computations for a spacing of 1000 ft, an error of 114,000 yd can be expected.
- Physical and Dynamic Oceanography