The Matlab computing environment has become a popular way to perform complex matrix calculations, and to produce sophisticated graphics output in a relatively easy manner. Large collections of Matlab scripts are now available for a wide variety of applications and are often used for university courses. The GPS Easy Suite is a collection of ten Matlab scripts, or M-files, which can be used by those just beginning to learn about GPS. The first few scripts perform basic GPS calculations such as converting GPS Time in year/month/day/hour/ minute/second format to GPS week/seconds of week, computing the position of a satellite using a broadcast ephemeris, and computing the coordinates of a single point using pseudorange observations. The latter scripts can perform calculations such as computing baseline components using either traditional least-squares or a Kalman filter, fixing cycle slips and millisecond clock jumps, and computing ionospheric delay using carrier phase observations. I describe the purpose of each M-file and give graphical results based on real data. The Matlab code and the sample datasets are available from my website. I have also included additional text files (in pdf format) to discuss the various Time Systems and Coordinate Systems used in GPS computations, and to show the equations used for computing the position of a satellite using the ephemeris information broadcast from the satellites.
Global Positioning System (GPS) is a term which is already included in dictionaries and designates the system that permits the location of an emitting source located on the Earth by the use of a satellite network. The book is devoted to this subject and at the same time to the Galileo System, a forthcoming European satellite-based navigation system. Both of them belong to the Global Navigation Satellite System (GNSS). The exposition is given in the frame of the Software-defined Radios, which designates a technology which is based on a flexible open-architecture receiver that permits to build a dynamic connection of various modules. The work of this platform is described in a MATLAB coding language.To have an idea of the included topics, we give its contents:
Snapshot techniques are based on computing a position using only a set of digital signal samples captured over some milliseconds. Existing techniques require, in addition to the satellite ephemerides, a rough knowledge of the position and/or time at which the snapshot was captured. We propose a new method to instantaneously compute a snapshot position and time solution without any reference time or position. The method is based on the addition of a fifth unknown to the instantaneous Doppler equations, which accounts for a time difference between the reference time and the measurement time. Using this new system of equations at different initialization times separated by some hours, time uncertainties of days or weeks can be solved. The algorithm has been implemented in a snapshot GPS software receiver in MATLAB, proving that position accuracies of a few meters with time uncertainties of several weeks can be obtained in a few seconds.
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