Abstract
The first order horizontal control network of Saudi Arabia, which is a purely terrestrial network established in early 1970's by EDM traversing, is analyzed for distortions. The analysis is based on comparisons of the terrestrial network positions with those obtained from a 22 point GPS network uniformly covering the country. An analysis of the discrepancies in slant ranges obtained from the two networks indicates that the terrestrial network scale is smaller than that of the GPS network by about 1.68 parts per million (ppm). The scale appears to change with position suggesting some small systematic distortion of the terrestrial network relative to the GPS network. A similar analysis of the discrepancies in horizontal distance, azimuth and zenith distance also points to some non-uniformities, albeit small ones, in the terrestrial network. The discrepancies appear to be position-dependent and hence non-random in character. The maxima of the magnitudes are 2.5 ppm, 0''.4 and 2''.7 respectively for the discrepancies in horizontal scale, azimuth and zenith distance.