The Global Positioning System (GPS) has become the main tool in positioning and Earth measurement applications, and its accuracy relies in the precise knowledge of the satellite orbits and time. Different approaches have been developed to estimate the receiver position. In this paper a non-recursive point solution approach algorithm is proposed for the receiver position estimation. The receiver position is estimated without considering the various error sources namely satellite clock bias, atmospheric delay, error in the broadcast ephemeris data, multipath error and receiver tracking error. The results are analyzed by computing the mean position (), standard deviation () and variance () over a period of the day and the results obtained are very promising. The error analysis is carried out by collecting the several days of dual frequency (1575.42 MHz and 1227.6 MHz) GPS receiver data from the Andhra University Engineering College, Visakhapatnam (Latitude/Longitude 17.73^o/83.32^o). The position error analysis studied in this paper will be helpful to surveyors and GPS Aided GEO Augmented Navigation (GAGAN) users over the Indian subcontinent in determining the obtained position accuracy over the 24 hour period particularly for aircraft purposes.

Global Positioning System (GPS) is an all weather, line-of-sight radio navigation and positioning system. GPS was developed primarily for military purpose. The multipurpose usage of NAVSTAR GPS has developed enormously within the last three decades. With the elimination of Selective Availability (SA) on May 2, 2000, the usefulness of the system for civilian users was even more pronounced. The system became fully-operational in 1994 (Bradford and James, 1996). Currently there are 32 operational satellites in the constellation. The GPS consists of three major segments: Space, control and user (Pratap and Per, 2001). The space segment consists of a nominal 24 operational satellites, which are constantly orbiting the surface at an altitude of approximately 3 Earth radii, and broadcast signals which travel at approximately the speed of light. Each satellite has a unique identification number. The control segment monitors the health and status of the space segment. The user segment consists of antennas and receiver processors which receive the signals broadcasted by the satellites, and decode them to provide precise information about the receiver's position and velocity. There are two fundamental GPS observables: the pseudorange, and the carrier phase, which can be used to estimate the receiver position.

Different approaches have been developed to solve the system of nonlinear Equation (1), some involving closed-form solution and some through linearization (Farrell and Barth, 1999). Since these approaches involve calculation of the receiver position from a single measurement of pseudoranges, they are called point solution approaches (Joseph and Erik, 2002). An algorithm is proposed based on the closed form point solution method and is described below. The proposed non-iterative algorithm requires less computational time compared to the conventional iterative algorithms such as recursive least squares and Kalman filter (Seiji and Toshiyuki, 2006).

Telecommunications Journal, Receiver Position Error Analysis, Global Positioning System, Earth Measurement Applications, Conventional Iterative Algorithms, Pseudorange Errors, GPS Receiver, Point Position Approach Algorithm, GPS Data, Pseudorange Nonlinear Equations, Satellite Orbits.