Abstract: This paper discusses the methodology to process single epoch GPS observations for deformation surveys. It takes full advantage of the characteristics of deformation surveys, i.e., the position of a surveyed point changes relatively small between two consecutive survey epochs. Special attention is given to efficient solution of carrier ambiguities and multipath effects. The tests indicate the methodology works well and an accuracy of a few millimeters is achievable. The developed method can be used to process the GPS data from both slow deformation and rapid/dynamic deformation monitoring.