Epoch-Differenced Cycle Slip Resolution Technique Considering Velocity Constraint

Carrier phase cycle slip detection and repair technology is one of the key technologies of high precision GNSS positioning. Carrier phase cycle slip cause the discontinuity of carrier phase observations. If the cycle slip can not be detected, which would draw an extra bias into positioning model with a minimum level of decimeter. Although, using a single epoch RTK algorithm can avoid the influence of carrier phase cycle slip, the method relies on high precision pseudorange observations or priori coordinates and it does not apply to the general high precision RTK positioning, especially for the single-frequency receivers. No doubt, the cycle slip detection and repair technology is vital for high precision carrier phase positioning. In order to satisfy the precision of sub-meter even centimeter RTK positioning with a low-cost single-frequency GNSS receiver, this paper proposes a cycle slip resolution method, which used velocity constraint information based on the carrier phase epoch-differenced model. First, we use Doppler observations to estimate the velocity of the current epoch, using the last epoch computed velocity, we can get the mean velocity between epochs, and multiply the mean velocity by the time difference between adjacent epochs, we can obtain epoch-differenced position increments vector. Then we can use the position increments as virtual observations, detect cycle slip with a modified data snooping method combined with the carrier phase epoch-differenced observations. Compared with the method only use the carrier phase epoch-differenced observations, more observation information is used with the velocity constraint information, and the accuracy and reliability of the detection result would also be improved. Experimental results show that the proposed epoch-differenced cycle slip resolution method can be effectively used in low-cost single-frequency RTK positioning.