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 115×112 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. / V članku je obravnavano vrednotenje geostatističnega modela ploskve za pretvorbo elipsoidnih višin, pridobljenih z meritvami GPS, v ortometrične višine. V raziskavi je bilo uporabljenih 1148 referenčnih točk, katerih višine so bile določene z geometričnim nivelmanom in meritvami GPS. Zajeto je območje velikosti 115 x 112 kilometrov v okviru projekta »Geodetska infrastruktura območja Izmir za izdelavo digitalnih fotogrametričnih zemljevidov in ortofotov v merilu 1 : 5000«. Osnovne podatke pomenijo razlike med elipsoidnimi in ortometričnimi višinami, ki so modelirane z metodo geostatistične interpolacije, in sicer krigingom. Uporabili smo programsko orodje ArcGIS 10.0 ’Geostatistical Analyst’ z optimiziranimi parametri modeliranja. Kakovost modela je bila analizirana z navzkrižnim preverjanjem, delitvijo podatkov in njihovim zunanjim preverjanjem. Ocenjena natančnost modela je približno 5 cm absolutno in približno 1 ppm relativno. Tudi skladnost modela z drugimi modeli geoida, in sicer z modeloma TG03 (turški geoid 2003) in EGM08 (Earth Gravitational Model 2008), znaša približno 7–10 cm.