Abstract:While the theory and implementation of geographic information systems (GIS) have a history of more than 50 years, the development of dedicated educational tools and applications in this field is more recent. This paper presents a free and open source software (FOSS) approach for education in the geospatial disciplines, which has been used over the last 20 years at two Italian universities. The motivations behind the choice of FOSS are discussed with respect to software availability and development, as well as educational material licensing. Following this philosophy, a wide range of educational tools have been developed, covering topics from numerical cartography and GIS principles to the specifics regarding different systems for the management and analysis of spatial data. Various courses have been implemented for diverse recipients, ranging from professional training workshops to PhD courses. Feedback from the students of those courses provides an invaluable assessment of the effectiveness of the approach, supplying at the same time directions for further improvement. Finally, lessons learned after 20 years are discussed, highlighting how the management of educational materials can be difficult even with a very open approach to licensing. Overall, the use of free and open source software for geospatial (FOSS4G) science provides a clear advantage over other approaches, not only simplifying software and data management, but also ensuring that all of the information related to system design and implementation is available.

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ABSTRACT:The task of conservation and management of cultural heritage is quite central in Italy, which lists a high number of beautiful architectures. A quick and precise survey may be requested in case of calamity. In the present paper, the most commonly used survey techniques are discussed, focusing on their applications for the conservation of the artistic heritage in case of emergency. Particular attention is given to Unmanned Aerial Systems (UAS) photogrammetry and its potentiality in obtaining good results in terms of speed, cheapness, precision and accuracy, assuring at the same time the safety of the operators in critical situations (e.g. natural disasters). A case study, realized at the Castle of Casalbagliano (Alessandria, Italy), is discussed. Different image block configurations and acquisition geometries (nadiral and oblique images) have been exploited, with the aim of defining useful guidelines for emergencies UAS survey of partially collapsed structures. An application to a significative case study is introduced.

ABSTRACT:The spread presence of GNSS Permanent Station Networks makes satellite surveys simpler, quicker and cheaper, and the achievement of high precisions easier. However, the result of a GNSS campaign benefits from an accurate planning, especially in presence of natural or artificial obstructions that make satellite observations difficult. Most of the GNSS office suites provide planning tools to analyze the satellite's visibility; visibility plots, sky plots and DOP charts are commonly built from the GNSS almanac. They usually allow planning on single points, taking into account the obstructions due to terrain morphology or buildings by hand-drawing polar diagrams after a visit of each location to be surveyed. This task can be made fully automatic by using a digital surface model to build the obstruction plot and the almanac to evaluate satellites' positions, hence their visibility, in a GIS. The procedure may be applied to whole areas to find the best time for the survey campaign. Taking a step further, this approach has been made available as a service by creating a Web Processing Service, which allows also non GIS specialists to access this tool through a simple WebGIS interface. The user can select the satellites constellation, GPS or GPS and GLONASS, the cut-off elevation angle, the day, hour and temporal window of the survey. The service returns raster maps describing the minimum number of visible satellites and the PDOP index in every pixel. Moreover, the service implements some features of the UNAVCO TEQC software, which can help to choose the location of new permanent stations. The implementation follows the OGC specifications and relies fully on FOSS software, combining different systems to provide the user web interface, the data storage and the processing engine. The service features, the underlying technology and some examples will be presented in this paper.

Integrated remote sensing techniques, such as photogrammetry from unmanned aerial vehicles (UAV), mobile laser scanners (MLS) and multibeam echosounders (MBES), are particularly effective in detecting and measuring coastal and seabed features and their modifications over time (4D analysis) induced by sea storms. In fact, these techniques allow the production of very high-resolution 3D models, with a continuum between above and below sea level. The present research is focused on the area of Portosole Marina (Sanremo, Western Liguria), affected by a severe sea storm in October 2018 and the following restoration. Two integrated 3D surveys were performed in February 2019 and in November 2019, obtaining accurate and reliable high-definition digital surface models (DSMs) in both emerged and submerged areas. The comparison between the two surveys highlighted volumetric changes in the seabed induced by the sea storm and the effects of a temporary worksite on the emerged and submerged breakwater. In particular, a total deficit of sediments of about 5000 m3 caused an average lowering of about 4 cm over the entire area, concurring with the breakwater instability. This study aims to contribute to the understanding of coastal system resilience within ongoing global climate changes, that is, increasing the intensity of extreme events in the Mediterranean area.

An optimized planning and realization of the survey, coupled with well thought-out processing, allows obtaining good quality results, while guaranteeing a reasonable use of resources and time. It represents a benefit for both operators and end-users. The former can save time and acquire smaller datasets to process, while the latter can invest their resources better. These goals are even more important in case of an emergency, because the circumstances can quickly change, causing risk to both people and goods. The paper examines the possibility of using Unmanned Aerial Systems (UAS) photogrammetry for 3D modelling in such scenario, focusing on finding a compromise between the final accuracy and the requested processing time. An experimental test has been conducted over the Castle of Casalbagliano, a damaged structure located near Alessandria (Piedmont, Italy), simulating a postemergency scenario. Several processing strategies have been tested to define a workflow useful in this kind of situations. The quality of the different processing has been evaluated in terms of both residuals of the bundle block adjustment and quality of the generated dense point cloud, compared with a reference Terrestrial Laser Scanner acquisition. Finally, the possibility of publishing the obtained 3D models on the web has been exploited too.

ABSTRACT:The conservation of Cultural Heritage depends on the availability of means and resources and, consequently, on the possibility to make effective operations of data acquisition. In facts, on the one hand the creation of data repositories allows the description of the present state-of-art, in order to preserve the testimonial value and to permit the fruition. On the other hand, data acquisition grants a metrical knowledge, which is particularly useful for a direct restoration of the surveyed objects, through the analysis of their 3D digital models. In the last decades, the continuous increase and improvement of 3D survey techniques and of tools for the geometric and digital data management have represented a great support to the development of documentary activities. In particular, Photogrammetry is a survey technique highly appropriate in the creation of data repositories in the field of Cultural Heritage, thanks to its advantages of cheapness, flexibility, speed, and the opportunity to ensure the operators' safety in hazardous areas too. In order to obtain a complete documentation, the high precision of the on-site operations must be coupled with an effective post-processing phase. Hence, a comparison among some of the photogrammetric software currently available was performed by the authors, with a particular attention to the workflow completeness and the final products quality.

ABSTRACT:GPS data from 181 permanent stations extracted from different networks covering France and the Italian part of the Alps are used to estimate a homogeneous set of tropospheric parameters over 14 years (from January 1998 to May 2012). The tropospheric zenith delay (ZTD) quantified in the GPS data analysis is closely related to the value of integrated water vapor above each GPS station. GPS ZTD is already successfully used for operational weather prediction and meteorological analyses, providing valuable data to improve our comprehension of the tropospheric water cycle and in particular to improve the prediction of precipitations. Moreover, GPS tropospheric measurements are intrinsically stable, so that long term observations represent a significant contribution to climatological studies. The results of a homogeneous reanalysis of up to 14 years of data with MIT's GAMIT/GLOBK software version 10.4 are presented. The estimated tropospheric parameters are 1 ZTD every 2 hours and one couple of horizontal tropospheric gradients (NS and EW) every 3 hours for each of the 181 stations, simultaneously with a daily positioning solution. A quality check of the tropospheric parameter time series identifies offsets, for example due to instrument changes at individual sites. The resulting verified time series can further be used for meteorological and climatological studies that go beyond the geodetic work presented here. Thanks to the length of the data set in time, a regional climatological approach could permit identifying specific patterns of ZTD variation that are related to severe weather events. The regional GPS stations could then contribute to an early warning system.