الفهرس 
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Abstract
The aim of the present study was to analyze the results of the set of daily measurements of levelling under different meterological conditions, performed simultaneously above different terrain covers or different heights of the insttrument. The efficiency of temperature models was estimated by comparing the daily variation of the measured temperature with those calculated according to different interpolation functions. significant discrepancies frequently occurred, particulary btween the measured and derived gradients. comparisons of the daily variation of the measured refraction errors lii with errors calculated form 12 different formulas again enables their efficiency. only in 6 formulas were the errors found to be within acceptable limits. (within the limits of 0.02 mm and 0.054 mm). In order to estimate the mean random coponents and mean effect of systematic factoes in the total error E in the measured height, atwo - factor analysis of variances of measured errors LiJ was performed according to the following equation: Eij= - Lij= Δij + Aj + B i where, Aj is the systematic terrain or height componet of which the same value affects the daily variation of the refraction error in a given sight line or heights. this is dependent on the different degree of absorption of the same heat flow or thermal radiantion of adifferent cover of the terrain and on the different meaqn value of the gradient in the different heights of acertain sight line above the terrain. B i is the systematic time componet, the same value of which affects all sight kine above different terrains or certain sight line in different heights. it is dependent on the intensity of the heat flow and changes with the time of the day. Δij= Eij + Δρ i j; it is the total random component of the total error in the measured height. The two- factor analysis of variances enable anumercal estimation of mean square errors SΔ, SÂ, S b and total mean errors Sl in the measured height under different meteorogical conditions. the mean systematic errors reach as much as 0.2 mm and usually exceed the effect of random error. Finally, investigations of the temperature field near buildings showed atypical models of the temperatre field which are asynthesis of vertical and horizontal gradients arising during absorption of the heat flow of the surface of bothe the terrain and walls.