Abstract：Integer ambiguity is affected by atmospheric delay error and it is difficult to correctly fix integer ambiguity for low elevation angle satellite between BDS reference stations. We propose the algorithm of triple-frequency ambiguity resolution for low elevation angle satellite between BDS reference stations. The advantage of long wavelength for extra-wide-lane integer ambiguity is used to determine double difference extra-wide-lane integer ambiguity. The double difference wide-lane integer ambiguity is searched and solved using the closer characteristic of ionospheric delay error between wide-lane combination observations. The linear relationship of double difference integer ambiguity is selected as a constraint condition, double difference integer ambiguity for high elevation angle satellite is searched and determined using dual-frequency ionosphere-free combination observation. The space linear model of double difference ionospheric delay error between reference stations is established using fixed double difference integer ambiguity for high elevation angle satellites, and the ionospheric delay error for low elevation angle satellites is weakened. Double difference carrier phase observation equation with fixed double difference integer ambiguity for high elevation angle satellite is selected as distance constraint, double difference integer ambiguity for low elevation angle satellite is searched and determined. This algorithm is tested by the measured triple-frequency data of BDS CORS network. The results indicate that triple-frequency integer ambiguity for low elevation angle satellites between BDS reference stations can be fixed accurately with the method.
