The accuracy data presented in the technical specifications of the geodetic surveying instruments produced by various companies are controversial. To be able to say anything about the accuracy of these data, they must be obtained under similar conditions, tested by process, adjusting and appropriate statistical methods, and then compared. In this study, Geodetic GNSS receivers produced by different companies were tested according to horizontal accuracies. However, vertical observations were also obtained, only horizontal accuracies were compared.. For this purpose, a horizontal control network was established and long-term static sessions were held with the instruments of each company in this network. The data obtained as a result of the sessions were converted into data files in the same format and adjusted separately by processing with the commercial software of one of the instruments. As a result of adjustment, the results obtained from the instruments of each company were compared according to the horizontal accuracy criteria.