Determination of Orthometric Heights from GPS and Levelling Data

One of the major tasks of geodesy is the determination of geoid. This task is getting more crucial due to the development of global positioning systems (GPS). This is due to the fact that GPS provide ellipsoidal heights instead of orthometric heghts. To convert ellipsoidal heights into orthometric heights, precise geoid heights are required. Nowadays, the most effective universal technique used for the determination of orthometric heights is the GPS and Levelling technique. This paper focuses on this technique and multiple regression analysis method was used to further determine the geoid undulations .ArcGIS 9.2 software was used for generating the grid map of the area using the corrected orthometric heights obtained by the regression method. The regression parameters a0, x1 and x2 were obtained as 1166.721268, -0.00085137265 and -0.00089422771399 respectively. From the analysis, the standard error of estimates S?1 and S?2 associated with x1 and x2 were obtained as 0.0001291688765 and 0.0001351270512 respectively. The coefficient of multiple determination R2 was found to be 0.992049442. the computed F-statistic was 5157.59101, while the value from F-distribution table was 3.97. Hence, the parameter estimators ?1 and ?2 are good estimates of the actual regression parameters x1 and x2.