On low-cost GNSS observables under different grades of antennas: Receiver-related biases and RTK results

Abstract

Low-cost receivers are becoming mainstream devices for providing positioning, navigation and timing (PNT) services that are accessible to the public. In contrast to existing advances, it is inappropriate for less-rigorous functional models and rough systemic error models, including the unknown characteristics of receiver-related biases (RRB) caused by internal hardware and the indefinite impact of an external antenna, to restrain the development of low-cost global navigation satellite system (GNSS) receivers. In this work, a comparative analysis was conducted to assess the respective effects of the internal hardware and an external antenna on low-cost receiver observables. We reparameterized a single-differenced geometry-based functional model and adopted a least squares filtering method to estimate RRB, including inter system biases (ISB), differential code biases (DCB), differential phase biases (DPB). First, an abnormal phenomenon was reported that the C099-F9P receiver showed better performance than the Trimble receiver on RRB when a U-blox ANN-MB antenna was used. Second, comparing the DCB and the DPB results, we found that the negative effect of the external antenna on the code observables is stronger than that on the phase observables. The standard deviation (STD) of the L1-L2 and E1-E5b DCB from the C099-F9P receiver reach 0.160 and 0.129 m, respectively, when the ANN-MB antenna is used. When connected to a higher-grade antenna, the low-cost receivers show DCB estimates stability similar to the Trimble receivers, where the L1-L2 and E1-E5b DCB STDs can reach 0.078 and 0.076 m, respectively. Third, it should be noted that the L1-L2 and E1-E5b DCB will change if a low-cost receiver restarts or is powered off. Fourth, of the DPB STDs of the low-cost and Trimble receivers connected to three different grades of antennas maintain agreement and reach 0.007 cycles or better. The phase observables can be free from the effect of the antenna in short-term case. Above all, the comparison results illustrate that low-cost GNSS receivers have the potential for high-precision applications and achieve an accuracy level and ability similar to high-grade receivers in mass applications when a survey-grade or higher-quality antenna is equipped.