The first main motivation of this thesis is using the GPS data to compute the orthometric height by simple polynomial techniques and filter the data by least square method using Matlab program. Control vertical networks consisting of ellipsoidal, orthometric and geoid height data are investigated. Although the theoretical relationship between these height types is simple in nature discrepancies among the combined height data, its practical implementation has proven to be quite challenging due to numerous factors that cause, with particular emphasis on (i) modeling a technique to compute the geoid undulation from GPS and precise leveling, (ii) correcting the observed geoid undulation by least square method. To address these challenges, a general procedure involving empirical and statistical tests for assessing the performance of selected parametric models is developed. Additional numerical studies include the obtained of geoid models (local geoid), scaling the GPS-derived ellipsoidal height matrix, and evaluating the orthometric heights obtained from national/regional adjustments of leveling data. Finally, the used technique with special mathematical and adjustment models gives good results for the middle and east of Egypt.