The Oceanographic Institute maintains a working Station at Cananéia in the southern coast of the State of S. Paulo. It is a lagoon region in a great extent occupied by mangrove swamps that offers many interesting aspect from the economical (fishing) and biological (variety of fauna and flora) points of view. Strong erosion processes are taking place and the coastal contour is rapidly being altered together with the navigation channels and sand banks as well. For hydrographical purposes and the development of routine control work several geodetic marks were established to serve as reference points. The author presents a map which is a graphic study of the region. The instrument used in this work was a "Watts" n.º 1 theodolite and the original "croquis" was drawn to a scale of 1:20,000 which gives a maximum error allowance of 20 meters.
