An approach of gross error elimination in GNSS receiver hot start

With the rapid development of the GNSS receiver's performance, almost all the commercial receivers have the ability of hot start. The main algorithm of fast positioning is how to get the position before frame synchronization when hot start. Because of the incomplete information of the pseudorange calculation before frame synchronization, the pseudorange is calculated by its estimation of integer millisecond part and inside millisecond part. If the estimation is wrong, the position error will be huge because of the huge pseudorange error, and it need to be researched and improved further. Firstly, the principle of fast positioning when hot start is introduced, the estimation and combination of pseudorange before frame synchronization and the correction of the position of satellite because of the unknown of the send time are derived in detail. The influence of the shift of general position and coarse receiver time error to fast positioning is discussed, the result shows the accuracy of fast positioning when the shifting is not abnormal and original least squares are nearly the same. When the pseudorange combination is just in the middle of a millisecond, a little shift of general position and coarse receiver time error will lead to a huge estimation error in pseudorange. For the gross error coming from the misestimating of the pseudorange, robust least squares are proposed to correct the gross error, the result of the simulation shows it's an effective way to correct the gross error.