الفهرس 
The intermediate orbitOnly 14 pages are availabe for public view
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Abstract
The global positioning system is designed so that at least four satellites are usually visible any geographical location.
One of its basic aims is the precise determenation of the geodetic coordinates of points of interest in an adopted Earth Fixed-Earth Central coordinate system. This could be accomplished by taking into account so many considerations. Some of these considerations are the geometrical ones which should be taken into account either in the geometric mode or in the dynamic mode.
The geometric mode at which the observed satellite positions are treated as auxiliary indendent points in space and they are ony used to relate the observations geometrically forming space network. Each observation relates the position of the observing stations together with the observed satellite position at each observing epochs.The number of observations should be sufficient to solve for the unknown station coordinates. The process described necessitates the usage of simultaneous observations(Pavlis 1982, Liek 1994)without any reference to that the motion of the satellite obeys the physical law of dynamics.As a result, in certain cases critical configurations (Blaha 1971) could appear although the number of observations in sufficient. Since the geometric solution does not depend on the dynamics of the satellite orbit. It does not affect by the imperfection of the orbital models.
In contrast to the geomtric methods, the observed satellite position in the dynamic method are not treated as auxiliary independent points in space but rather they are constrained to be in aspace curv(Dedes 1987). This curve should resemble within the required degree of accuracy the satellite orbit under question.Dynamic modeling resulting in three second order differential equations or six first order differntial equations refrred to as equation of motion of the satellite (chap. 3). These differential equations are integrated either analytically or numerically to generate the satellite orbit .
In this investigations the Dynamic point positioning method will be implemented using GPS satellites range observations collected from single frequency receiver to study the effect of orbit/station/earth geometry on the accuracy of the base lines coordinates. The dynamical analysis gives the advantage of observing each each orbit separately rather than the geometric analysis which requires at least four observed satellites to give the point coordinates.
Since our concern is the geometry not to estimate GPS orbital parameters with highest acuuracy,perturbing factors such as gravitational perturbations higher in degree and order than j2, perturbations due to atmospheric drag, solar radiation pressure, attraction in this investigatuion.With these assumptions in mind the observation time span will be minimized to recover for the time depedent neglected parameters (moving stations in an non rigid earth).
The practical motivation behind this investigation is that, since we have many options in the tracking geometry different shapes and locations of GPS satellite passes) are available, it is required to specify some practical considerations for observing the satellites which products the best results for the adjusted coordinates.Some of these considerations besides the orbital geometry are, the length of the tracking baselines, conditions site tracking or multiple site tracking, the period of site occupation, the time frequency of the observations, the number of receivers, the minimum cut off angle after which the satellite is allowed to be observed, anf all posible ways for minimizing the coordinates. With these factors in mind a se of geometrical considerations which give best geometrical strength to the least squares solution to be the points coordinates and some times to the baselines will be listed. The observations are simulated GPS range observations assumed to be collected from a signal frequancey (L I band) receivers.