GNSS Robust Positioning Algorithm Research And Its Application In Consumer-Grade Receivers

In this paper,three different GNSS positioning modes are implemented for different levels of precision requirements of consumer receivers: Standard Point Positioning(SPP),real-time dynamic short baseline pseudorange double difference relative positioning(Real-Time Differential,RTD),and real-time dynamic short baseline pseudorange and carrier phase double difference relative positioning(RealTime Kinematic,RTK).The latter two are based on virtual reference station information provided by local Continuously Operating Reference System(CORS)and network RTK service to enhance consumer receiver rover positioning.At the same time,for the problem of multiple pseudorange gross errors of consumer receivers and multiple cycle slips in single-frequency situations,this paper proposes a forward backward robust positioning method based on excluding or initializing per satellite,which is applied to multi-system GNSS SPP,RTD,RTK to improve positioning accuracy and reliability.Firstly,the feasibility of this paper's software and algorithm,and the performance of the robust SPP,robust RTD and robust RTK are evaluated by a single-frequency multi-system static simulation dynamic experiment.The experimental results show that the gross error or cycle slip can be correctly detected and identified when only one satellite has pseudorange gross error or carrier cycle slip,and the robust positioning solution is 100% available,and the external accuracy is the same as the solution from the original none-gorss observation.When 20% satellites(3 to 4 satellites in this paper)have pseudorange gross errors,both SPP and RTD maintain 100% gross error detection rate and 0 false alarm rate.The correct recognition rate of SPP is 98.75%;and for RTD,the compeletely correct recognition rate of gross error is 98.89%,and the correct recognition rate of gross error is 99.16%,which is partially improved compared with SPP,and is the effect of double-difference pseudorange robust supplement.When 20% satellites have cycle slips,the robust RTK maintains a 100% cycle slip detection rate and a zero false alarm rate.Although the correct recognition rate of the cycle slip drops to 81.36%,some of the epochs are only two satellites in a single system and one of them is set to cycle.No matter which one is reinitialized,the positioning result is not affected.The remaining failure epochs were also reinitialized by all satellites,maintaining the accuracy of the single epoch solution and maintaining availability of 100%.When 40% of the satellites(6-8 satellites in this paper)have gross errors in the pseudoranges,or 40% of the satellites have cycle slips in the carrier phases,they can still maintain the 100% detection rate and the 0 false alarm rate.However,the correct recognition rate will drop to 56.33% for SPP,56.88% for RTD and 32.2% for RTK.To improve such extreme situation,the multi-frequency data or more information sources are needed.Finally,the GNSS robust positioning method under multiple gross errors verified above is used to evaluate the true dynamic positioning performance of the Ublox consumer receiver,and the service capabilities of this method for consumer-grade receivers.The vehicle dynamic experiment results of the single-frequency dual-system Ublox M8 T show that,the RTK plane accuracy reaches 0.23 m and the elevation reaches 0.21 m,which meets the decimeter-level positioning requirements.For the RTD,the accuracy of the plane is 0.61 m and the elevation is 0.93 m,which meets the sub-meterlevel positioning requirements.The SPP plane accuracy reaches 1.67 m and the elevation reaches 0.53 m,which meets the meter-level positioning requirements.The single-frequency single-system Ublox EVK7 P handheld walking dynamic experiment results show that,its RTK plane accuracy is 0.78 m and the elevation accuracy is 0.88 m.The RTD plane accuracy is 1.42 m and the elevation accuracy is 2.16 m.The SPP plane accuracy is 1.50 m and the elevation accuracy is 4.48 m.In this case,it needs RTK positioning mode to meet the plane and elevation sub-meter-level positioning requirement.In the RTD and SPP positioning modes,it can meet the meter-level positioning requirements.On the whole,in the case of multiple pseudorange gross errors and multiple cycle slips under single-frequency,the GNSS robust positioning method performs well.According to the scenario,accuracy requirements and availability requirements,combined with the reference station information acquisition cost,network link situation,computing power and other cost or accidental factors,the consumer-grade rover user can select the robust SPP,RTD or RTK positioning mode,and obtain the plane and elevation position services of different precision levels such as meter,submeter and decimeter.