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Title: Improved Ambiguity Function Method applied to GPS static deformation monitoring
Authors: Lau, Ki-yuen Lawrence
Degree: M.Phil.
Issue Date: 2000
Abstract: This project aims to investigate a fast and precise GPS processing algorithm suitable for short-baseline static deformation monitoring in short observation time-span. The slow displacement of static deformation can provide a fairly good a priori position determined in the previous measurements, which can be used as the approximate position for processing the new set of measurements. Ambiguity Function Method (AFM) is selected as the main data processing engine in this research. AFM has two advantages when applied to static deformation monitoring. Firstly, the search volume of AFM can be greatly reduced with a good a priori position, resulting in higher data processing efficiency. Secondly, Ambiguity Function is insensitive to cycle slips and computation of position using AFM does not require ambiguity resolution. However, AFM may result in an incorrect position when serious un-modeled errors and biases, such as multipath and ionospheric delay, are present in the measurements. Another disadvantage of AFM is that it has no direct and rigorous accuracy assessment for the positioning result. In this research, two improved AFM GPS data processing algorithms are proposed to improve the GPS relative carrier phase positioning accuracy. They are the Combined AFM and Least Squares Method (LSM) with signal-to-noise ratio weighting (CALMS), and Signal-to-noise ratio Weighted Ambiguity function Technique (SWAT). Tests have been done and show that these two processing algorithms can effectively mitigate specular multipath as well as interference in GPS relative carrier phase measurements by using signal-to-noise ratio. Investigations have also been made on an automatic and self-contained integrated GPS date processing algorithm, the integration of the above-proposed algorithms with Least-squares AMBiguity Decorrelation Adjustment (LAMBDA) method. The proposed integrated GPS data processing algorithm is applicable to process deformation measurements without a good a priori position. Test results show that integration of the above-proposed algorithms with LAMBDA can significantly reduce data processing time and provide extra statistical information on quality and reliability of processed results. The proposed processing algorithms have been programmed using Visual Basic 5.0. The programs and test data sets collected on the roof of The Hong Kong Polytechnic University and in the construction site of the Hong Kong International Airport at Chek Lap Kok were used for verification of the proposed algorithms. Accuracy assessments are compared with pre-defined displacements on a X-Y-Z stage and results of the same set of data computed using Trimble's GPSurvey WAVE baseline processing software.
Subjects: Global Positioning System
Hong Kong Polytechnic University -- Dissertations
Pages: xvi, 192 leaves : ill. ; 30 cm
Appears in Collections:Thesis

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