| Summary: | Tidal datums are important to determine for harbor safety issue. Using which, harbor dock and pool
depth can be safely designed. In case of an existing harbor, tidal datums can be used as reference for
depth of harbor pool. This research is intended to determine tidal datums of Sadeng harbor, one of the
harbors in the District Girisubo Gunungkidul, recommended for the safety of harbor based on tidal
data.This research was begun by measuring the depth and tidal elevation. The depth was measured using
fishfinder echosounder while tidal elevation was observed visually using tide staff during the survey.
Tidal data was processed to produce mean sea level (msl) value, harmonic constants, and the lowest low
water level predictions, namely Lowest Astronomical (LAT) the expected lowest low water. For
comparison, the one year IOC tidal data was used. The depth was corrected for transducer draft factor,
tidal factor, and the reference depth (low water). The expected result is the corrected depth referring to
LAT, for the safety of the ship in harbor. This study concluded that the minimum, maximum and average
depths of Sadeng pool are 0 meter, 4,28 meter, and 2,23 meter respectively after all corrections were
applied and the depths were referred to LAT. The difference between msl of IOC tidal data and of tidal
measurement is 0864 m, the latter being higher than the first one. The msl resulted from harmonic
analysis of IOC tidal data is 1,425 m. The predicted LAT is 0.252 meter. Hence, reduction from msl to
LAT is 1,006 m. Since the depth of 0 m exist in the pool, the area with the respectivedepth is quite
dangerous for ships to pass through it. Dredging sediment is one solution.
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