Model geoida je eden od sestavnih delov državnega koordinatnega sistema. Poleg dokaj razširjenega določanja nadmorskih višin na podlagi GNSSizmere pa model geoida zagotavlja tudi kakovostnovključitev terestričnih geodetskih opazovanj v državni koordinatni sistem. Za GNSS-višinomerstvo je treba na podlagi modela geoida določiti geoidne višine, pri terestrični geodetski izmeri pa je poleg geoidnih višin treba določiti tudi vrednosti odklonov navpičnic.Določitev geoidne višine na podlagi modela geoida je v praksi zelo razširjena naloga, medtem ko se z določitvijo vrednosti odklonov navpičnice v praksi zelo redko srečamo. V prispevku predstavljamo metodo določitve vrednosti odklonov navpičnice z določitvijolege tangencialne ravnine glede na ploskev geoida v točki. Lego tangencialne ravnine glede na elipsoid, s katerim je podan tudi odklon navpičnice v točki, izračunamo na podlagi interpoliranih geoidnih višin v neposredni okolici obravnavane točke. V prispevku smokakovost računsko pridobljenih odklonov navpičnic primerjali z merjenimi in celoten postopek ovrednotili na praktičnem primeru.; The geoid model represents part of the national coordinate system. It can be used for the purpose of GNSS-levelling, but the use of geoid heights also improves incorporation of terrestrial observations intothe state coordinate system. In GNSS levelling tasks, geoid heights are obtained from the geoid model, but with terrestrial observations the deflection of the vertical is also needed. Determination of geoid heights from the geoid model is a simple engineering task; however, determination of deflection of the vertical is not so common in geodetic practice. The purpose of this paper is to present the localmethod of establishing the deflections of vertical with the help of a plane, which is calculated on the basis of interpolated geoid heights. The coefficients of the plane give the deflection of the vertical in the point of gravity. This means that, given a known geoid, we can calculate the deflection of the vertical at any point in the region of Slovenia. Comparison of calculated deflections with the measured deflections was performed in order to estimate the accuracy of the proposed procedure. The procedure was tested in thegeodetic network with four points.