Many research studies have tried to improve the techniques for effective control of changes in coastal spaces caused by natural or human-induced phenomena. Such alterations modify the capacity for natural regeneration of beaches, and because of the growing population in these areas coastal management must pay close attention to the subject. The method used in this study case at Sauaçui Beach establishes a terrestrial digital model using topographic software fed by a georeferenced data bank generated by a three-dimensional global positioning system (GPS) whose vertical coordinates are referred to as tidal datum. The GPS technology can be used for the accommodation dynamic of the earth's crust of tectonic displacements. This method is able to identify the level curve equivalent to the maximum elevation of the wave run-up line, as well as the position of the waterline, during any stage of tidal elevation through curves of higher or lower levels of elevation, depending on the specific need of the study. Besides determining a baseline for future observations at Sauaçui Beach, this study allows us to evaluate the occurrence of alterations in the volume of sediments at the beach through differences among the generated land surfaces during different periods of time, as well as the risk of substantial variations in the shoreline position caused by eventual sea-level changes.