In this paper a new approach for producing precise hydrographic charts is addressed. This goal is achieved by solving the problem of removing tidal and heave effects from hydrographic depth sounding without applying costal tide gauge observations which could be quite erroneous at places with complicated tidal regimes like the gulfs. Two driving forces of our machinery are (1) precise 3-D GPS positions during the hydrographic operations, and (2) application of tidal models derived from satellite altimetry missions. For the precise GPS positioning double difference carrier phase observations can be used. The tidal models derived from satellite altimetry could be used to compute precise Local Chart Datum (LCD). Here we define the Local Chart Datum as the lowest sea water level due to tide at the sounding point. Having, (1) the precise position of depth sounding transducer, (2) measured depth from sounding, the local chart datum can be derived for the coordinates of sounding location, by using the tidal model derived from satellite altimetry. Next, using the aforementioned pieces of information the sounding depth with respect to local chart datum can be derived as follows: . It is important to note that in this way we are not only reducing the soundings to the chart datum, but also removing the effect of heaves during the sounding process. This procedure, specially, in waterways connected to oceans, and with low depth of water, like Persian Gulf can be very helpful for producing accurate and reliable hydrographic charts. As the case study, 11-years of Topex-Poseidon satellite altimetry data is used to produce a hydrographic chart for a test region at Persian Gulf. It is important to note that the average depth in Persian Gulf is meters and the tide effect in some places can reach to meters, therefore could be regarded as challenging test areas for improving the water depth information presented in a hydrographic chart. Our numerical tests indicate a considerable improvement in the produced hydrographic chart based on our proposal. In summary, main achievements of this study could be listed as: (1) removal of the heave effect from the soundings, (2) removal of the tidal effect from the soundings, and (3) a new proposal of definition of chart datum, i.e. Local Chart Datum.
)