Performance Analysis of a Positioning Algorithm Using Raw Measurements Taken from a GPS Receiver

The scope of this paper is the implementation of a positioning algorithm using the approach of post-processing the measurements taken from a real GPS receiver, in order to assess user´s position and performance of the algorithm. Recently, there is an increase interest in positioning techniques based on Global Navigation Satellite Systems so we focus on the performance evaluation of a positioning algorithm. The current method of solving for GPS user´s position is to linearize the pseudorange equations and calculate the user position iteratively, starting with a user provided initial position guess. We implement an Iterative Least Squares (ILS) algorithm by means of data structures and show that five iterations are required to obtain a convergent solution. The algorithm automatically combines all available GPS pseudorange measurements when more than four satellites are observed. Experimental results show that reliable absolute positioning is achieved by using the algorithm. By weighting each satellite´s contribution in user position evaluation process by means of Carrier-to-noise-density ratio (C/No) is achieved an improvement on the position estimation mostly in the vertical component.