The purpose of this study is evaluation of geostatistical surface model for transformation of GPS derived ellipsoidal heights to orthometric heights. The model was handled as its accuracy for surveying applications. 1148 reference points were used covering an area of 115x112 km with GPS and leveling data from the "Izmir geodetic infrastructure for the production of 1/5000 scaled digital photogrammetric maps and orthophotos" project. As a basic data, the differences between ellipsoidal and orthometric heights for each benchmarks were modeled by geostatistical interpolation method namely kriging. ArcGIS 10.0 Geostatistical Analyst was used with optimized parameters for modeling. The quality of the model was analysed by Cross Validation, splitted data and external data validation. The model provide about +/- 5 cm absolute, 1 ppm relative accuracy Also the consistency of the model with several geoid models namely TG03 (Turkish Geoid 2003) and EGM08 (Earth Gravitational Model 2008) geoids was approximately +/- 7-10 cm.