Improved Knight Method Based on Narrowed Search Space for Instantaneous GPS Attitude Determination

Abstract

ABSTRACT:The Knight algorithm can instantaneously resolve integer ambiguities and improve significantly the search speed by skipping over most less-likely integer ambiguity candidates. However, its reliability relies on the volume of the integer ambiguity search space.Utilizing coarse attitude knowledge can reduce the size of the search space. This paper proposes a new method to narrow the search space by taking into account a geometric constraint of visible satellites. The constraint is formulated as a recursive procedure and is thus very suitable to be incorporated into the search loop of the Knight method. Experimental results demonstrate that the proposed method can improve the search efficiency and reliability of the Knight method.

High precision GPS positioning with multiple receivers using carrier phase technique and sensor fusion

“…In a practical case the covariance matrix of ∇∆µ k is hard to define only from the measurements of ∇∆φ k . Therefore methods [5], [15], [17] which require this covariance matrix usually produce false positive result from a single epoch measurement.…”

“…Although there are also methods which can determine the integer ambiguity from a single measurement, but in this case the number of false positive results is high [15].…”

“…1 They require the knowledge of the correlation matrix of the carrier phase measurements [17], [15].…”

Ambiguity Function Method Scheme for Aircraft Attitude Sensor Utilising GPS/GLONASS Carrier Phase Measurement

“…As one of the important ambiguity resolution on-thefly (OTF) approaches, the ambiguity function method (AFM) uses only the fractional value of the instantaneous carrier phase measurement, so the ambiguity function values are insensitive to the whole cycle change of the carrier phase or cycle slips [4][5][6]. In attitude determination, fixed-length baseline is used to constrain the ambiguity resolution in AFM process.…”

Closed-Form ADOP Expressions for Single-Frequency GNSS-Based Attitude Determination

“…A widely used approach for this is the integer least-squares search as implemented in the LAMBDA method, see e.g. Han et al (1997), Park and Teunissen (2003), Dai et al (2004) and Li et al (2005). For successful ambiguity resolution it is required that the probability that the estimated integer solution coincides with the correct integers (the ambiguity success rate) is sufficiently high.…”