Strategy for Single-Epoch RTK Positioning Using Dual Frequency in Urban Areas

The rapidly increasing demand for high-precision positioning has prompted researchers to develop real-time kinematic (RTK) techniques. In urban areas, however, global navigation satellite system (GNSS) signals are susceptible to obstruction, reflection, and diffraction by dense foliage and buildings, leading to a reduction in the number of tracked satellites and a degradation of GNSS raw measurements due to nonline-of-sight (NLOS) signals and multipath errors. This, in turn, increases the difficulty of accurately resolving integer ambiguities. To address this issue, this article proposes a combined strategy to exclude satellites contaminated by NLOS or multipath. Based on the combined strategy, two single-epoch ambiguity resolution methods, proposed method 1 (PM1) and proposed method 2 (PM2), are introduced. Three kinematic field tests conducted in different typical urban environments are used to validate the effectiveness of the proposed strategy. The correctly fixed means a less than 0.1 m 3-D positional error. The results indicate that, with a mask angle of 10 degrees, the correctly fixed rates of PM1 and PM2 are 96.0% and 97.0% in scenario 1, 63.9% and 64.4% in scenario 2, and 55.9% and 62.7% in scenario 3, respectively. These rates are higher than those of comparative method 1 (CM1) and comparative method 2 (CM2), which are 79.6% and 85.7%, 32.9% and 45.0%, and 29.9% and 45.0% in scenarios 1, 2, and 3, respectively. When the mask angle increases to 20 degrees, the correctly fixed rates of PM1 and PM2 are 96.8% and 97.6% in scenario 1, 63.9% and 64.5% in scenario 2, and 56.8% and 63.9% in scenario 3, respectively. Compared to CM1 and CM2, this represents an improvement of between 7.8 and 27.4% points.