Method in Determining Vessel Attitude with GPS

With the development of the GPS positioning technology, GPS is widely applied in the field of hydrographic surveying.The high accuracy of GPS in determining 3D coordination ensures high accuray of parameters of vessel attitude in measuring vessel attitude.In this paper, the effects of vessel attitude for depth are discussed systematically.It is found that the effect of dynamic squat for depth is direct and more large than the effects of pitch and roll of vessel for depth.The limitation of traditional model of computing dynamic squat is analyzed.A new model is given in this paper. In order to saitsfy the accuracy and simple procedure of survey in determining vessel attitude, the technologies of GPS, carrier phase measurement and OTF are applied in the research.Using these technologies, the accuracy about ±5cm in plane direction and ±3cm in height direction is validated in test.It shows that the method of determining vessel attitude is feasible. Because of the direct effect of tide for depth, it must be considered in calculating vessel attitude.In the procedure of getting tide value, tidal observation and the interpolation of tide are used.At the same time, the interpolation model of tide is given in this paper. By the above processing, the following conclusions are got:①the method that GPS carrier wave phase differential survey technology is used for determining vessel attitude is avaicable.②dynamic squat is mainly affected by velocity, meanwhile, the mean depth in surveying area, the static squat, shape of vessel, wind and wave also have some contribution to dynamic squat.③pith and roll are got by the respective height difference between GPS antennas at bow and center of vessel. The above methods were used in Yangze River.A satisfactory result is given in this paper.