Integrating elevation and bathymetric data in GIS for a continuous 3D model of Ischia Island and surrounding seabed

3D models, particularly useful in many technical and scientific applications, can be easily created starting from cartographic data, using the tools provided by Geographic Information Systems (GIS). If you want to create a 3D model concerning both the territory and the marine areas adj acent to it, the necessary cartographic data are often present in different documentary sources. This requires some preliminary operations in order to homogenize these data, bringing them to the same cartographic datum, proj ection and scale of representation. This article aims to define an efficient procedure for the construction of a 3D model of Ischia Island and the surrounding seabed at medium scale. For the territorial part, a Digital Elevation Model (DEM) with a resolution of 2 meters is used. For the bathymetric part, the data is taken from an Electronic Navigational Chart (ENC) at a scale of 1:30,000. The two types of data differ both in the detail of information and in the altimetric datum. The territorial data is processed in order to have the elevation information at the same scale of representation as the nautical chart. The bathymetric data is traced back to the same altimetric datum of the DEM. The elevation and depth data, reported at the same projection (Universal Transverse of Mercator, UTM) and datum (WGS84), are interpolated by Ordinary Kriging imposing a resolution of 15 meters. The verifications of the level of accuracy through Cross-validation confirm the validity of the procedure performed and the quality of the model obtained.