Bathymetric survey shows a digital model of topographic surface of sea bottoms with different resolution according to the instrument used and underwater depth. Bathymetric survey is used during construction of harbour with basis placed on riverbed or sea bottoms for drafting cables and geomorphologic valuation of riverbed and lake basin. We can calculate volumes,return sections, distances and anything else as information about sea bottom. We realize tridimensional maps. Surveyrealized by a natant with a ecosounding-lead (to see sea bottom’s depht) one beam or more beam, supported by a GPS placed on natant and calculates the position in relation to a GPS placed on earth.