Аннотация:The atmospheric boundary layer can change the trajectories of rays from celestial objects in the course of observations because the parameters of the layer are dependent on the time of day. In the present paper, an attempt is made to assess possible errors arising in meridional observa-tions, owing to the slope of sur-faces of equal density. Formulas are derived to obtain corrections for refraction caused by a thin atmospheric layer having a large angle of slope with respect to the earth's surface.