Phase Ambiguity Resolution Method Using Processing of Code and Carrier Phase Pseudoranges in a Kalman-Type Filter

The main problem of implementing high-precision pseudoranges by carrier phase lies in their ambiguity associated with the ambiguity of the phase measurements of the navigation receiver. Thus, the development of new methods for phase ambiguity resolution becomes a very important element of high-precision positioning. The paper considers relative methods for estimating the coordinates of a stationary object that involve the use of both user and base (network in the case of a network of base receivers) receivers with precisely known coordinates located at a distance of several thousand kilometers from each other. We propose an algorithm for phase ambiguity resolution (integer type) based on the use of a Kalman-type filter (KTF), which receives ionosphere-free combinations of code and carrier phase pseudoranges. It is shown that traditional methods of ambiguity resolution require a significant observation period (about 2,000 seconds). We propose a method for evaluating the linear combination of phase ambiguities in the L1 and L2 bands obtained from instantaneous phase measurements. Its application along with the estimation of KTF parameters makes it possible to resolve phase ambiguities from as early as 50 seconds of observation. Set forth are the results of an experiment, in which code pseudorange measurements are used prior to the resolution of phase ambiguities and carrier phase pseudorange measurements are used after ambiguity resolution.

Computer model of high-precision navigation of a small satellite constellation for remote Earth sensing tasks

One of the key tasks in the formation of the small satellite constellation is to ensure its stable configuration in time. The specific of this problem lies in the fact that the task must be solved in real time with sufficiently high accuracy with significant restrictions on the power consumption of onboard satellite systems. The paper briefly discusses one possible approach of secondary signal processing and solving the navigation and ballistic tasks, which involves the joint use of code, phase measurement methods, integer phase ambiguity resolution, and inter-satellite measurements.

PPP and PPP-AR Kinematic Post-Processed Performance of GPS-Only, Galileo-Only and Multi-GNSS

Precise point positioning (PPP) has been used for decades not only for general positioning needs but also for geodetic and other scientific applications. The CNES-CLS Analysis Centre (AC) of the International GNSS Service (IGS) is performing PPP with phase ambiguity resolution (PPP-AR) using the zero-difference ambiguity fixing approach also known as “Integer PPP” (IPPP). In this paper we examine the postprocessed kinematic PPP and PPP-AR using Galileo-only, GPS-only and Multi-GNSS (GPS + Galileo) constellations. The interest is to examine the accuracy for each GNSS system individually but also of their combination to measure the current benefits of using Galileo within a Multi-GNSS PPP and PPP-AR. Results show that Galileo-only positioning is nearly at the same level as GPS-only; around 2–4 mm horizontal and aound 10 mm vertical repeatability (example station of BRUX). In addition, the use of Galileo system—even uncompleted—improves the performance of the positioning when combined with GPS giving mm level repeatability (improvement of around 30% in East, North and Up components). Repeatabilities observed for Multi-GNSS (GPS + GAL) PPP-AR, taking into account the global network statistics, are a little larger, with 8 mm in horizontal and 17 mm in vertical directions. This result shows that including Galileo ameliorates the best positioning accuracy achieved until today with GPS PPP-AR.

The Coarse-Position-Free Coarse-Time Positioning Method for BDS Receiver

The Coarse-Time Positioning method is important for the quick positioning of the BeiDou Navigation Satellite System (BDS) navigation receiver in the weak signal environment. The coarse position estimation is the key technology of the Coarse-Time Positioning (CTP) for the BDS navigation receiver without coarse position assistance. In this paper, a Coarse-Position-Free Coarse-Time Positioning method based on mixed-type code phase ambiguity resolution is proposed. In this CTP method, in order to estimate the approximate position, the coarse position estimation method based on the mixed-type code phase ambiguity search is used. This method does not require any additional external auxiliary position information to complete the coarse position estimation. Based on the real observation data and dynamic simulation observation data, the test experiment is designed. According to the error of coarse position estimation, the positioning accuracy, and the success rate of the coarse-time solution, the Coarse-Position-Free Coarse-Time Positioning (CPFCTP) method of the BDS receiver based on the mixed-type code phase ambiguity resolution is evaluated. The experimental results show that, when the coarse-time deviation is within 30 s, the CPFCTP method has a success rate of over 97%. When the coarse-time deviation is within 5 s, the success rate of positioning is 100%. At the same time, the experimental results also show that, for the situation that the navigation signals of some BeiDou satellites are completely occluded, the CPFCTP method proposed in this paper can obtain the correct code phase ambiguity and still maintain a high success rate of CTP at the same time.