Project founded by eContentplus Programme Magistrato alle Acque di Venezia Provision of interoperable datasets to open GI to EU communities MAGISTRATO ALLE ACQUE DI VENEZIA Elevation model September 2008 Magistrato alle Acque di Venezia Project founded by eContentplus Programme

Provision of interoperable datasets to open GI to EU communities 2 A Digital Terrain Model (DTM) is a numerical representation of a surface based on a set of X, Y and Z coordinates. The surface represented by the MAV elevation model is the Venice lagoon water system made up of channels and shallows, mud flats and salt marshes. MAV Elevation model – Introduction Z Height (elevation) values Depth values

The location of salt marshes in the Venice Lagoon Provision of interoperable datasets to open GI to EU communities 3 Two images of mud flats during a low tide Salt marshes in the northern lagoon MAV Elevation model – The Venice Lagoon water system

The DTM is based on the results of a bathymetric and topographic survey realized by the Venice Water Authority six years ago in the Venice Lagoon. A TIN (Triangulated Irregular Network) was carried out from the input data using a planar interpolation. The TIN (.ttn file) was then converted into a GRID (.grd file) Provision of interoperable datasets to open GI to EU communities 4 MAV Elevation model – How

Horizontal reference system GAUSS BOAGA Fuso est Ellipsoid and Datum: INTERNATIONAL (HAYFORD) - ROMA40 Vertical reference system the elevation values (meters) are referred to the national average sea level (Genoa 1942). Provision of interoperable datasets to open GI to EU communities 5 MAV Elevation model – Reference Systems

Input data Terrain Feature Type: Regular Points Elevation points which describe the morphology of the Venice Lagoon. They are the result of a bathymetric and topographic survey realized using different measure methodologies. Provision of interoperable datasets to open GI to EU communities 6 MAV Elevation model – Imput data

- Terrain Feature Type: Drains 3-D linear features that represent the lines connecting the maximum depth points of each channel and they are based on the bathymetric survey results. - Terrain Feature Type: Breaklines 3-D linear features that represent the edges of lagoon channels and they are also based on the bathymetric survey results. - Terrain Feature Type: Obscure areas 2-D polygons around areas for which no elevation data is available. They are one of the input data to build the Terrain Model, but no triangulation can take place in an obscure area Provision of interoperable datasets to open GI to EU communities 7 MAV Elevation model – Imput data

Provision of interoperable datasets to open GI to EU communities 8 MAV Elevation model – Some uses TIN Contour lines Depth contours Bands Cartographic use The new hydrographic map of the Venice Lagoon

The grid model is used to compare the results of different surveys and to monitory processes like erosion and sedimentation in the Venice Lagoon. Provision of interoperable datasets to open GI to EU communities 9 MAV Elevation model – Some uses

Correspondence between INSPIRE and MAV Elevation features Provision of interoperable datasets to open GI to EU communities 10 MAV Elevation model – INSPIRE Core data: DEM and/or DTM as regular grid, indifferent solutions, for land and sea bottom TIN (Triangular Irregular Network) Additional data: Contour line and depth contour - Altitude Breakline - category (crest, thalweg, other) Spot height - altitude - category (summit, …) - name Sounding - altitude High and low water line INSPIRE elevation features type and attributes MAV elevation features type and attributes Core data: DTM as regular grid for land and sea bottom (50X50m, 10X10m, 5X5m) TIN (Triangular Irregular Network) Additional data: Contour line and depth contour (derived product) - Altitude Breakline - category (only edges of channels) Drains - category (only lines connecting the maximum depth points of each channel) Regular points - altitude - relief year - relief methodology - code Obscure areas

Provision of interoperable datasets to open GI to EU communities January 2008 Provision of interoperable datasets to open GI to EU communities Project founded by eContentplus Programme Thank you Magistrato alle Acque di Venezia