| With the Bei Dou-3 officially providing global service capability,the development and application of GNSS entered a new era.As one of the research hot spots in GNSS field,real-time PPP technology is mainly applied on land.GNSS high-precision positioning is much less widely used in sea.The main reason is that these high-precision positioning techniques require communication to transmit data.However,the satellite communication is mainly used to transmit data in the ocean and the cost is high.Nowadays,with the extensive development and utilization of Marine resources,the human needs for satellite precision navigation and positioning technology are increasingly extensive.As one of the features of BDS,short-message communication provides a new choice for realizing the data transmission between land and ocean.Bei Dou short-message can realize two-way communication through GEO,and the service cost is low.However,Bei Dou short-message communication has the following problems in the process of data transmission:the communication length of each short-message is limited to 628 bits;the communication frequency of ordinary users is limited to 60 seconds.In order to realize the real-time precise point positioning in the ocean,this paper focuses on these two issues and conducts the following research.(1)RTS data quality assessment.In order to realize Ocean Real-time Precise Point Positioning with Bei Dou short-message communication,first,the quality evaluation of RTS data,including the availability of data,the precision of real-time precision products,and the location accuracy and convergence time of IGS station.Through analysis,it is found that the positioning accuracy of the four systems is the best and the convergence time is the shortest.(2)In order to solve the limitation of Bei Dou short-message communication length,the RTS data simplification scheme is proposed.Experiments have been carried out to verify the feasibility of this scheme.Experiments show that taking 9 satellites each GNSS as an example,one short message can send the RTS data of two systems,and two short messages can send the RTS data of four systems.(3)In order to overcome the problem of Bei Dou short-message communication frequency,solve the problem by forecasting satellite.precision products only minute-interval RTS corrections are sent and for data outside the minute interval,short-time forecasting scheme is used to solve the problem.The experimental results show that this method can meet the positioning accuracy requirements.(4)Experimental test and analysis.the IGS station and practical ocean observation data is used to simulate the data encoding sending,receiving though Bei Dou short-message and decoding.The post processing method by simulating real-time applications is used to calculate the position of the user.Experiments show that the Real-time PPP through Bei Dou short-message can achieve an accuracy within 10 cm in horizontal directions,and an accuracy of better than 20 cm in vertical direction,which can meet the requirements of many navigation and positioning applications in Ocean. |
