Effect of ocean tides on the determination of zenith delay

GPS meteorology is a new field in GPS applications, in which precise determination of zenith delay is a key component. A strong correlation exists between the vertical displacement caused by ocean tide and the zenith delay at a given GPS station, so the effect of ocean tide on the precise determination of the zenith delay can not be neglected. We have processed and analyzed the GPS data of the Crustal Motion Observation Network of China from Day 10 to Day 40 of 2001, and the result shows that such effect varies over a range of several millimeters. For example, it is ± 7mm for the coastal station at Shanghai and ±1 mm for the inland station at Wuhan at maximum.