A positioning method and a system are disclosed for measuring a position of a vehicle on land, air, and space, using measurements from a global positioning system receiver and an inertial measurement unit. In the present invention, an integrated Kalman filter processes the all-available measurements of the global positioning system: pseudorange, delta range, carrier phase, and the solution of an inertial navigation system. The integrated Kalman filter is a multi-mode, robust kalman filter, in which optimal integrated mode is selected based on the measurement availability and filter stability. The high accurate solution of the inertial navigation system, which is corrected by the Kalman filter, is used to aid on-the-fly resolution of the carrier phase integer ambiguity of global positioning system in order to incorporate the carrier phase measurements into the Kalman filter, and to aid the carrier phase and code tracking loops of the receiver of the global positioning system to improve the receiver jamming and high dynamic resistance.

Fully-coupled positioning process and system thereof

A real-time algorithm to detect, determine, and validate the cycle-slips for triple-frequency GPS is proposed. The cycle-slip detection is implemented by simultaneously applying two geometry-free phase combinations in order to detect more insensitive cycle-slips, and it is applicable for high data rate applications. The cycle-slip determination adaptively uses the predicted phase data and the code data. LAMBDA technique is applied to search for the cycle-slip candidates. The cycle-slip validation provides strict test criteria to identify the cycle-slip candidates under low phase noise. The reliability of the proposed algorithms is tested in different simulated scenarios.

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Instantaneous Triple-Frequency GPS Cycle-Slip Detection and Repair

In this contribution the integrity of single- receiver, single-channel, multi-frequency GNSS models is studied. The uniformly most powerful invariant test statistics for spikes and slips are derived and their detection capabilities are described by means of minimal detectable biases (MDBs). Analytical closed-form expressions of the phase-slip, code-outlier and ionospheric-disturbance MDBs are given, thus providing insight into the various factors that contribute to the detection capabilities of the various test statistics. This is also done for the phaseless and codeless cases, as well as for the case of a temporary loss-of-lock on all frequencies. The analytical analysis presented is supported by means of numerical results

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Single-receiver single-channel multi-frequency GNSS integrity: Outliers, slips, and ionospheric disturbances

Single-frequency GNSS RTK is a promising technology in the popularization application due to its relative low expense compared to multi-frequency RTK. Owing to the incapability of forming between-frequency combination and the relatively poor quality of single-frequency receivers, particularly for low-cost receivers, the cycle slip estimation in single frequency is a significant challenge. We propose a new efficient method for real-time single-frequency cycle slip estimation by imposing position-based polynomial constraint based on a fact that the motion of vehicle often obeys a low-order polynomial over a short period. The key is to precisely model the motion kinematics by means of a low-order polynomial fitting of several historical epochs. With the constraint of positional polynomial, the estimation of cycle slips can be significantly improved. To evaluate the feasibility and reliability of this method, a variety of cycle slip situations are tested by comparing with two traditional methods, i.e., the measurement-based polynomial fitting and the triple-differenced residual-based method. The results show that the new method can achieve better results than two traditional methods.

Single-frequency GNSS cycle slip estimation with positional polynomial constraint

The ubiquitousness of location-based services has proven effective for many applications such as commercial, military, and emergency responders. Software-defined radio (SDR) has emerged as an adequate framework for the development and testing of global navigational satellite systems such as the global position system (GPS). SDR receivers are constantly developing in terms of acceleration factors and accurate algorithms for precise user navigation. However, many SDR options for GPS receivers currently lack real-time operation or could be costly. This paper presents a LabVIEW (LV) and C/C++-based GPS L1 receiver platform with real-time capabilities. The system relies on LV acceleration factors as well as other C/C++ techniques such as dynamic link library integration into LV and parallelizable loop structures, and single instruction, multiple data methods, which leverage host PC multipurpose processors. A hardware testbed is presented for compactness and mobility, as well as software functionality and data flow handling inherent in LV environment. Benchmarks and other real-time results are presented as well as compared with the other state-of-the-art open-source GPS receivers.

Development of a Real-Time Software-Defined GPS Receiver in a LabVIEW-Based Instrumentation Environment

In order to use pure carrier-phase measurements, the initial ambiguities of the measurements have to be solved. Once obtained, these ambiguity solutions can be lost by shadowing, short-time loss of lock on one or several satellites and other effects, commonly referred to as cycle-slips. Restarting the ambiguity resolution algorithm is a time- and computation-intensive task and should be avoided as long as possible. In order to compensate for such short interruptions, an algorithm would be desirable which detects cycle-slips and is able to correct their magnitude for the individual measurements. In this paper an algorithm is presented which detects, using the redundancy inherent in the GPS-measurements, any cycle-slips. The residuals between the Doppler measurement and a calculated Doppler based on a least-squares solution show significant changes whenever cycle-slips occur. Determining in which channel the cycle slip occurred and calculating its size is possible using external information, for instance an INS-system. Instead of using the least-squares solution, the short-term stability of the INS-system is utilized to generate the calculated Doppler. Results are presented for such an integrated system showing the effectiveness in correcting even multiple simultaneous cycle-slips down to the loss of one cycle. The effects of decreasing satellite redundancy on the effectiveness of the algorithm and the influence of the information supplied by the INS system on the quality of the cycle-slip repair are investigated. Since GPS and INS sensors work in a closed loop for correction of the cycle-slips, error detection at this stage is essential for reliable operation of the integrated navigation system. >

X. Gu

Papers

Cycle-slip detection and repair in integrated navigation systems