Research on Linear Combination Models of BDS Multi-Frequency Observations and Their Characteristics

The linear combination of multi-frequency carrier-phase and pseudorange observations can form the combined with special properties. type number frequencies will directly affect characteristics observations. BDS-2 BDS-3 broadcast three five signals, respectively, study their is great significance for precision positioning. In this contribution, in cycles meters sorted out. Seven frequency modes are formed, some combinations positioning searched. Then, based on principle minimum noise, a simpler search method optimal real coefficients ionosphere-free (IF) least squares (LS) proposed. general analytical expressions geometry-based (GBIF), geometry-free (GFIF), multipath (PMP) first-order ionosphere delay taken into account derived. And expression derivation process given when both second-order ionospheric delays eliminated. Based this, coefficient various compared discussed. reflect that accuracy from dual-frequency (DF) to five-frequency (FF) gradually improving. becomes significantly larger after taking account. addition, better than BDS-2. When only considered, attribute (B1C, B1I, B2a) best among triple-frequency (TF) BDS-3. B3I, recommended.