Interpolation of single beam echo sounder data for 3D bathymetric model

Transmitting sound waves into water, and measuring time interval between emission and return of a pulse, single beam echo sounder determines the depth of the sea. To obtain a bathymetric model representing sea-floor continuously, interpolation is necessary to process irregular spaced measured points resulting from echo sounder acquisition and calculate the depths in unsampled areas. Several interpolation methods are available in literature and the choice of the most suitable of them cannot be made a priori, but requires to be evaluated each time. This paper aims to compare different interpolation methods to process single beam echo sounder data of the Gulf of Pozzuoli (Italy) for 3D model achievement. The experiments are carried out in GIS (Geographic Information System) environment (Software: ArcGIS 10.3 and its extension Geostatistical Analyst by ESRI). The choice of the most accurate digital depth model is made using automatic cross validation. Radial basis function and kriging prove to be the best interpolation methods for the considered dataset

Comparison of different interpolation methods for DEM production

Spatial interpolation, or the estimation of the variables at unobserved locations in geographic space based on the values at observed locations, is fundamental in all geophysical sciences, first of all for the construction of digital elevation model (DEM). Several methods are available in literature for spatial interpolation and the choice of the most suitable of them for building DEM, depends on many factors, particularly on the distribution of the sampled points, therefore, on the morphology of the area to be mapped. This paper aims to choose the most appropriate interpolators for DEM production, by comparing different methods usually available in GIS software. For the purpose of developing the best performing model and comparing interpolators, a set of elevation data collected by digital vector map is used. The accuracy of interpolation methods is tested by analyzing 4 statistic parameters, which are achieved by cross-validation leave-one-out. Particularly, minimum, maximum, mean and root mean square error (RMSE) are calculated for each interpolation method considering the residual in each sampling point between measured and interpolated value

The importance of the coordinate transformation process in using heterogeneous data in coastal and marine geographic information system

Coastal and Marine Geographic Information Systems (CMGISs) permit to collect, manage, and analyze a great amount of heterogeneous data concerning coastal, sea, and ocean environments, e.g., nautical charts, topographic maps, remotely sensed images. To integrate those heterogeneous layers in CMGIS, particular attention is necessary to ensure the perfect geo-localization of data, which is a basic requirement for the correct spatial analysis. In fact, the above-mentioned types of information sources are usually available in different cartographic projections, geodetic datum, and scale of representation. Therefore, automatic conversions supplied by Geographic Information System (GIS) software for layer overlay do not produce results with adequate positional accuracy. This paper aims to describe methodological aspects concerning different data integration in CMGIS in order to enhance its capability to handle topics of coastal and marine applications. Experiments are carried out to build a CMGIS of the Campania Region (Italy) harmonizing different data (maps and satellite images), which are heterogeneous for datum (World Geodetic System 1984 and European Datum 1950), projection (Mercator and Universal Transverse of Mercator), and scale of representation (large and medium scale). Results demonstrate that automatic conversion carried out by GIS software are insufficient to ensure levels of positional accuracy adequate for large scale representation. Therefore, additional operations such as those proposed in this work are necessary

Accuracy of global geoid height models in local area: Tests on Campania region (Italy)

Nowadays GPS technology permits to reach millimeter or sub-millimeter horizontal relative accuracy levels over very long distances (up to hundreds of kilometers). The vertical GPS accuracy is more difficult to obtain. In addition, because GPS heights are referred to ellipsoid, their transformation into orthometric heights requires the use of a geoid model that influences with its accuracy the quality of the results. Usually a local geoid model is characterized by a high level of accuracy, but often it has a fee. Global geoid models are free available and their accuracy is to test in the local area where they are to use so to evaluate their suitability for the user purposes. This paper is aimed to compare different Global Geoid Models testing their accuracy on Campania region (Italy). Particularly, models respectively named EGM84, EGM96 and EGM2008, are considered and tested on 18 points corresponding to GNSS Permanent Stations in Campania. For the best resulting model, the EGM2008, a solution to improve further its performance is adopted

From electronic navigational chart data to sea-bottom models: Kriging approaches for the Bay of Pozzuoli

Electronic Navigational Charts (ENCs), official databases created by a national hydrographic office and included in Electronic Chart Display and Information System (ECDIS), supply, among essential indications for safe navigation, data about sea-bottom morphology in terms of depth points and isolines. Those data are very useful to build bathymetric 3D models: applying interpolation methods, it is possible to produce a continuous representation of the seafloor for supporting studies concerning different aspects of a marine area, such as directions and intensity of currents, sensitivity of habitats and species, etc. Many interpolation methods are available in literature for bathymetric data modelling: among them kriging ones are extremely performing, but require deep analysis to define input parameters, i.e. semi-variogram models. This paper aims to analyze kriging approaches for depth data concerning the Bay of Pozzuoli. The attention is focused on the role of semi-variogram models for Ordinary and Universal kriging. Depth data included in two ENCs, namely IT400129 and IT400130, are processed using Geostatistical Analyst, an extension of ArcGIS 10.3.1 (ESRI). The results testify the relevance of the choice of the mathematical functions of the semi-variogram: Stable Model supplies, for this case study, the best performance in terms of depth accuracy for both Ordinary and Universal kriging