The use of GPS receivers became popular anywhere in many fields. Different accuracies could be obtained from GPS to serve in different fields of applications. GPS could be used in navigation, point positioning, and differential modes by processing the code. On the other hand, GPS could be used in relative positioning (surveying mode) by processing the carriers (phase observations). Surveying mode serves practically as static and kinematic techniques of observations. The precision of the GPS techniques may be published in the manuals of the instruments. In this research, the precisions of the GPS techniques are practically investigated. The effects of many factors on the results of the GPS work are studied. GPS observations along the last five years and covering different places in Egypt are used in this study. The results of this research met the published results and some cases did not meet the published results.