حل سريع ابهام فاز به روش AFM در دريا

Modifying the AFM Method for the Solution of Phase Ambiguity at Sea Areas

Nowadays we can use Global Positioning Systems (GPS) for navigation and the establishment of pipe lines at the sea areas. Applications such as the establishment of pipe lines at sea area or 3D navigation in canals with narrow width need positioning with accuracy better than 1 meter. In such high accuracy applications, the main observable is carrier phase measurement. The main problem with carrier phase measurement is phase ambiguity. The solution of phase ambiguity is the under influence of cycle slip at the sea areas. There are two reasons for cycle slip at the sea area (1) multipath effect due to reflection of the received waves at sea surface near to antenna (2) fluctuations of the sea surface which exerts some acceleration on antenna. The majorities of phase ambiguity solution methods use least square but least square method is the under influence of cycle slip effect because it causes the divergence of the least square. Ambiguity Function Method (AFM) is a method which is safe against the cycle slip. Ergo in this research AFM method is proposed for phase ambiguity solution at the sea areas. AFM method applies for determination of a set of integer ambiguity. The algorithmic steps of AFM method is as follows: i) Approximate coordinate of the station. ii) Define a neighborhood with a special criterion near to station. iii) Compute ambiguity function for each candidate and store one with maximum value. iv) Compute integer ambiguity using coordinates from best solution. The topic of this paper is to modify AFM method as an efficient method for solving phase ambiguity in sea areas. Keywords: Phase Ambiguity, Navigation, Global Positioning System, Ambiguity Function Method