Abstract:

Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun and the rotation of the Earth. There are 3 systems tide: Mean Tide System, Zero Tide System and Free Tide System. This paper presents the tide and its effect on GPS-levelling and Altimetry. The paper also presents the experimental formula to compute the effect of the tide on heights. According to this formula, a correction due to the tide only depends on the latitude. The experimental results show that impacts of the tide to heights change from -6.3cm to -3.1cm in the VietNam. The differences of the tide impact to the heights of two different points is very small, hence does not affect on GPS-levelling. For Altimetry, the tide significantly affects in the sea surface height observations.