A New Ambiguity Resolution Method Applied to Uncombined Precise Orbit Determination

With the continuous refinement of multi-GNSS and multi-frequency data processing, there is an increasing interest for the observation model based on uncombined (UC) strategy. Ambiguity resolution is an important issue in the field of GNSS. The ambiguity fixing of wide-lane (WL) is based on the MW combination of pseudo-range and carrier phase observations, with the geometry-free and ionospheric-free (IF) characteristic. A significant disadvantage of MW combination is that it is contaminated by pseudorange observations. This study proposes a method that does not need to use MW combination to derive the WL ambiguity. Instead, the original UC float ambiguity is used to obtain the WL ambiguity. The float ambiguity obtained through parameter adjustment is measured using the carrier phase observation, which is more accurate than the MW combination observations. The new method is applied to the dual-frequency UC precision orbit determination experiment. The residual distribution of WL DD ambiguity is first analyzed, and results show that the new method is closer to the integer value than the residual distribution of the MW strategy. Then use the GPS observation data of about one month to verify orbital accuracy of the new method, and compare with results of the UC and IF strategies, respectively. Results show that the orbit and clock products obtained by the new method receive the best accuracy. The new method is also applicable to other UC ambiguity resolution situations, such as UC precise positioning.