| Summary: | 碩士 === 國防大學中正理工學院 === 軍事工程研究所 === 90 === One of the purpose for hydrographic surveying is accurately determining a sea topography. It should choose a reference level, leading the sounding data to be accurately reduced to this datum, that called sounding datum. Because sea surface change will affected by tide, it can take proper tidal observations to caculate the datum, besides it also can obtain by transfer techniques from vicinities long-term well-defined datum and some relative measurement.
The tests aimed at different representive areas tida gauges which separateed into three parts of western Taiwan, for example, Shin-chu Port, Tai-chung Port and Kao-hsiung Port, utilizing different terms（short-term, month-term, year-term）data for computing. It also use traditional way of datum transfer methods (height difference method, simultaneous observation method, range ratio method and least squres ratio method) to try to connect with adjacent for getting field datum.
From actual field test, we can get the average error is 11-14 cm for using one money term observation that is normal hydrographic survey schedule, but it cannot fit the IHO third calss specification of 10 cm. It will need more than one year term observation then cam catch up with 5 cm requests at least. During these ways when using short term observation, it only the least squres ratio method can reach to the IHO third calss standard claim.
This research tried to use GPS to transfer datum level, in order to establish one set of promoting precision method.
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