In 1990 the first mapping project of submerged aquatic rooted vegetation was carried out to determinate the coverage of three species of seagrasses (Zostera marina Zostera noltii and Cymodocea nodosa occurring in the Lagoon of Venice. After twelve years a new program of research has been started in the framework of a monitoring project carried by Consorzio Venezia Nuova, on behalf of Magistrato alle Acque, Venice. Part of this project deals with the update of seagrass map of Venice Lagoon. All shallow bottoms, tidal flats and channels (not deeper than 2.5 metre) of the Lagoon have been surveyed, as it was made for the previous mapping of 1990. Field operations have been carried out by boat, adopting a satellite positioning system with DGPS technology (accuracy: 1 metre) connected to a portable PC where all data collected in the field, concerning presence of the species, coverage percentage and other information about seagrass meadows have been recorded and daily downloaded to a desk station.