High resolution geomatics techniques for coastline detection and monitoring: Boccasette and Barricata case studies (Po River Delta, Rovigo, Italy).

The topic studied in this thesis aims to analyze an experimental approach for the definition of a methodology that allows the identification of the coastline, or instantaneous coastline, perceived as a land-sea-air interface. As we will see its geographical boundaries are not easily defined in a universal way, we will see through the comparison between three different methodologies, including the GNSS system the classical topography and the methodology of photogrammetric survey Sfm (structure from motion), the difficulties encountered in defining an extension to land and sea that delimits the coastline in a unique way. The treated area concerns areas on the Po delta, specifically the beaches of Boccasette and Barricata. In the chapters will be addressed the various aspects, first analyzing the context of reference, identifying the location, with an introduction to the coastal reality in question, characterized by phenomena such as subsidence, a worrying phenomenon for the Po delta area, monitored by several studies over the years. The various methodologies applied in the context will be explained, exposing the characteristics of the same to understand their potential in the case study, then passing to the software used to process data and obtain the output. The data obtained with the various methodologies have been compared with each other in GIS thanks to the potential that the software offers, proving practical and fast. The approach of the study mainly uses the distance and the area between the segments joining the points detected, evaluating the differences in terms of mean and standard deviation, to establish, also on the basis of the operator’s interpretation, which of the following methodologies is the most practical, precise and fast for monitoring purposes. We then went on to compare and discuss the results obtained with the various methods, highlighting the more or less significant variations. As we will see, there is a certain difference between the methodologies used directly in the field, by measuring the physical points and the Sfm technique, influenced as we will see by many factors. The coastline at zero level obtained through a DTM (Digital Terrain Model) was subsequently superimposed and compared with the coastline extracted from a LiDAR survey performed in 2018. This second activity allowed, through appropriate processing, a four-year multi-time analysis of coastline changes and the identification and classification of areas of expansion and erosion. The research thus made it possible to: - A comparison between the different methodologies comparing their applicability and limits; - Evaluate and define the most appropriate relevant technique to study and identify the coastline; - Define the accuracy parameters for modelling the detected elements; - The creation of a database for possible future comparisons of coastal variations; - The possibility of conducting a multi-temporal analysis with available LiDAR data.