For the determination of spatial coordinates of the points of a net-work a local Cartesian coordinate system is introduced, whoze z-axis coincides with the true vertical of an arbitrarily selected central point in the net-work, and whose x-axis is oriented to astronomical north. The observed horizontal directions and vertical angles, which refer to the local verticals of the observation stations, are reduced to parallels to the z-axis and the x-axis. For this purpose the direction of the local vertical in the observation stations and at least the astronomical azimuth of one side of the net-work need to be measured.