The main objective of this thesis is the construction of a corrective surface in theMoldova area for further conversion of the geodetic heights into normal heights. For thispurpose a detailed analysis of the optimal combination of heterogeneous height data ispresented, with particular emphasis on (i) modeling systematic errors and datuminconsistencies, (ii) separation of random errors and estimation of variance componentsfor each height type, and (iii) practical considerations for modernizing vertical controlsystems. Although the theoretical relationship between geodetic, normal heights andheight anomalies is simple in nature, its practical implementation has proven to be quitechallenging due to numerous factors that cause discrepancies among the combined heightdata. In addition, variance component estimation is applied to the common adjustment ofthe heterogeneous heights. This leads to the connection between the proper modelling ofsystematic errors and datum inconsistencies with the estimated variance components.Ultimately, one of the main motivations for this work is the need to introduce moderntools and techniques, such as GPS/levelling, in establishing a vertical control. Therefore,part of this thesis is aimed at bringing to the forefront some of the key issues that affectthe achievable accuracy level of GPS/levelling. Overall, the analysis of the optimalcombination of the heterogeneous height data conducted herein provides valuable insightto be used for a variety of height related applications.