The new Geodetic Reference System in Italy: an opportunity or a nuisance?

Maurizio Barbarella, "Il nuovo Sistema Geodetico Nazionale: una opportunità o un impiccio? = The new Geodetic Reference System in Italy: an opportunity or a nuisance?", in: Bollettino dell'Associazione Italiana di Cartografia, 153 (2015), pp.4-18Il Sistema di Riferimento di una nazione costituisce il linguaggio comune col quale esprimere la posizione dei dati geografici, in qualunque parte della nazione e con qualunque tecnica e qualunque precisione essi vengano acquisiti. Recentemente è stato introdotto in Italia dal Sistema di Riferimento Europeo ETRFOO secondo le indicazioni di INSPIRE e quindi nella prospettiva di facilitare l'interscambio dei dati geografici a livello di Unione Europea. Durante il Convegno ASITA tenutosi a Firenze nel 2014 i partecipanti a una Ta vola Rotonda hanno discusso le nuove prospettive che si aprono allacomunità che opera in ambito geomatico e la necessità di definire le modalità più appropriate e condivise per transitare al nuovo sistema, dalla realizzazione e manutenzione della rete che sostanzia il sistema geodetico, alla transizione dei dati pregressi al nuovo sistema di coordinate, all'interscambio dei dati. Nella Tavola Rotonda si è anche discusso il fatto che il Sistema di Riferimento non ha però la stessa valenza per tutti gli operatori: per alcune applicazioni l'inserimento in esso è centrale, anzi apre nuove prospettive, per altri è ininfluente e per altri è tutto sommato marginale, non privo di costi. In questo numero del Bollettino AIC i Relatori della Tavola Rotonda sviluppano le tesi e le informazioni presentate al Convegno. Questa nota in particolare presenta un quadro introduttivo al problema, oltre alle opinioni al riguardo dell'autore.A national Reference System is a common language which permits to express geographical data, no matter where they have been collected or with which technique or at what level of precision. Recently it has also been introduced in Italy the European Reference System ETRS89,Frame ETRFOO, in the perspective of facilitating the exchange of geographic data at EU. During the conference ASITA held in Florence in 2014 participants in a round-table discussed the new prospects opened up to the community which work in the geomatic field and therefore the necessity to define the most appropriate methods to transform the data prior to the new DATUM. The panel also discusses the fact that the reference system does not have the same value for all stakeholders: for some applications the inclusion in a reference system is central point for others it is irrelevant and for other is a phase altogether marginal and not at all costless. In this issue of the AIC Bulletin the Speakers develop the thesis and the information presented at the Conference. This note presents an introductory framework to the problem, as well as the opinions of the author about the subject

NEW SURVEYING METHODS FOR MAPPING

Nell’ambito delle attività finalizzate alla realizzazione di Cartografia e di Basi di Dati Territoriali, le moderne tecnologie mettono a disposizione tecniche di rilievo che, fatta salva la precisione necessaria alla scala della carta da costruire, consentono un alto livello di produttività. Una fase importante del processo di rilevamento della posizione dei punti utili alla realizzazione della Cartografia è quella dell’inquadramento nel Sistema Cartografico Nazionale. A questo proposito occorre considerare le novità intervenute nella definizione da parte dell’IGM del nuovo riferimento geodetico italiano, oggi incentrato nel frame denominato Rete Dinamica Nazionale. Nella nota si presentano alcuni elementi di recente introduzione nella pratica operativa del rilievo, ormai incentrato sull’uso di ricevitori satellitari, in particolare le strutture che consentono il rilievo di precisione in tempi brevissimi, le reti di stazioni permanenti interoperanti in tempo reale.The surveying of points to carry out the photogrammetric and mapping process can be done with modern techniques, subject to two principal requirements: to achieve the accuracy necessary for the scale of the map to be built, but also allowing a high level of productivity. In the process of acquisition of the points position is included the phase of insertion of the new network in the national geodetic frame and in the Cartographic System. In the note we present some innovative features: the current geodetic infrastructure (RDN) that allows the inclusion in the National Geodetic and Cartographic System, the evolution of the GPS technique, from static GPS baseline to the real time surveys allowed by the use of NRTK

Monitoring of large landslides by Terrestrial Laser Scanning techniques: field data collection and processing

We have monitored a large landslide that causes extensive damage by using Terrestrial Laser Scanners (TLS) and Global Positioning System (GPS) receivers. Our surveys have confirmed that the slope undergoes a continuous change. When using TLS some operational difficulties arise. We have used different TLSs types to better evaluate the reliability of our surveys; a full wave TLS has allowed to make easier the data filtering. All surveys have been framed in the same absolute reference system; this has been done by connecting both targets and laser stations to a Global Navigation Satellite System (GNSS) Permanent Reference Stations network. A direct comparison among the DEMs allows to infer the movements of the landslide

Assessment of DEM derived from very high-resolution stereo satellite imagery for geomorphometric analysis

ABSTRACTVery high-resolution satellite stereo images play an important role in cartographical and geomorphological applications, provided that all the processing steps follow strict procedures and the result of each step is carefully assessed. We outline a general process for assessing a reliable analysis of terrain morphometry starting from a GeoEye-1 stereo-pair acquired on an area with different morphological features. The key steps were critically analyzed to evaluate the uncertainty of the results. A number of maps of morphometric features were extracted from the digital elevation models in order to characterize a landslide; on the basis of the contour line and feature maps, we were able to accurately delimit the boundaries of the various landslide bodies

APPLICATION OF LIDAR-DERIVED DEM FOR DETECTION OF MASS MOVEMENTS ON A LANDSLIDE

In order to reliably detect changes in the surficial morphology of a landslide, measurements performed at the different epochs being compared have to comply with certain characteristics such as allowing the reconstruction of the surface from acquired points and a resolution sufficiently high to provide a proper description of details. Terrestrial Laser Scanning survey enables to acquire large amounts of data and therefore potentially allows knowing even small details of a landslide. By appropriate additional field measurements, point clouds can be referenced to a common reference system with high accuracy, so that scans effectively share the same system. In this note we present the monitoring of a large landslide by two surveys carried out two years apart from each other. The adopted reference frame consists of a network of GNSS (Global Navigation Satellite Systems) permanent stations that constitutes a system of controlled stability over time. Knowledge of the shape of the surface comes from the generation of a DEM (Digital Elevation Model). Some algorithms are compared and the analysis is performed by means of the evaluation of some statistical parameters using cross-validation. In general, evaluation of mass displacements occurred between two surveys is possible differencing the corresponding DEMs, but then arises the need to distinguish the different behaviors of the various landslide bodies that could be present among the slope. Here landslide bodies’ identification has been carried out considering geomorphological criteria, making also use of DEM derived products, such as contour maps, slope and aspect maps

Landslide monitoring using multitemporal terrestrial laser scanning for ground displacement analysis

In the analysis of the temporal evolution of landslides and of related hydrogeological hazards, terrestrial laser scanning (TLS) seems to be a very suitable technique for morphological description and displacement analysis. In this note we present some procedures designed to solve specific issues related to monitoring. A particular attention has been devoted to data georeferencing, both during survey campaigns and while performing statistical data analysis. The proper interpolation algorithm for digital elevation model generation has been chosen taking into account the features of the landslide morphology and of the acquired datasets. For a detailed analysis of the different dynamics of the hillslope, we identified some areas with homogeneous behaviour applying in a geographic information system (GIS) environment a sort of rough segmentation to the grid obtained by differentiating two surfaces. This approach has allowed a clear identification of ground deformations, obtaining detailed quantitative information on surficial displacements. These procedures have been applied to a case study on a large landslide of about 10 hectares, located in Italy, which recently has severely damaged the national railway line. Landslide displacements have been monitored with TLS surveying for three years, from February 2010 to June 2012. Here we report the comparison results between the first and the last survey

Kinematic GPS survey as validation of LIDAR strips accuracy

As a result of the catastrophic hydrogeological events which occurred in May 1998 in Campania, in the south of Italy, the distinctive features of airborne laser scanning mounted on a helicopter were used to survey the landslides at Sarno and Quindici. In order to survey the entire zone of interest, approximately 21 km2, it was necessary to scan 12 laser strips. Many problems arose during the survey: difficulties in receiving the GPS signal, complex terrain features and unfavorable atmospheric conditions. These problems were investigated and it emerged that one of the most influential factors is the quality of GPS signals. By analysing the origi¬nal GPS data, the traces obtained by fixing phase ambiguity with an On The Fly (OTF) algorithm were iso¬lated from those with smoothed differential GPS solution (DGPS). Processing and analysis of laser data showed that not all the overlapping laser strips were congruent with each other. Since an external survey to verify the laser data accuracy was necessary, it was decided to utilize the Kinematic GPS technique. The laser strips were subsequently adjusted, using the Kinematic GPS data as reference points. Bearing in mind that in mountainous areas like the one studied here it is not possible to obtain nominal precision and accu¬racy, a good result was nevertheless obtained with a Digital Terrain Model (DTM) of all the zones of inter¬est

Sentinel-2 Data and Unmanned Aerial System Products to Support Crop and Bare Soil Monitoring: Methodology Based on a Statistical Comparison between Remote Sensing Data with Identical Spectral Bands

The growing need for sustainable management approaches of crops and bare soils requires measurements at a multiple scale (space and time) field system level, which have become increasingly accurate. In this context, proximal and satellite remote sensing data cooperation seems good practice for the present and future. The primary purpose of this work is the development of a sound protocol based on a statistical comparison between Copernicus Sentinel-2 MIS satellite data and a multispectral sensor mounted on an Unmanned Aerial Vehicle (UAV), featuring spectral deployment identical to Sentinel-2. The experimental dataset, based on simultaneously acquired proximal and Sentinel-2 data, concerns an agricultural field in Pisa (Tuscany), cultivated with corn. To understand how the two systems, comparable but quite different in terms of spatial resolution and atmosphere impacts, can effectively cooperate to create a value-added product, statistical tests were applied on bands and the derived Vegetation and Soil index. Overall, as expected, due to the mentioned impacts, the outcomes show a heterogeneous behavior with a difference between the coincident bands as well for the derived indices, modulated in the same manner by the phenological status (e.g., during the canopy developments) or by vegetation absence. Instead, similar behavior between two sensors occurred during the maturity phase of crop plants

Topographic Base Maps from Remote Sensing Data for Engineering Geomorphological Modelling: An Application on Coastal Mediterranean Landscape

Coastal landscapes are one of the most changeable areas of the earth’s surface. Given this spatial complexity and temporal variability, the construction of reference maps useful for geo-engineering is a challenge. In order to improve the performance of geomorphic models, reliable multiscale and multi-temporal base maps and Digital Elevation Models (DEM) are needed. The work presented in this paper addresses this issue using an inter-geo-disciplinary approach to optimize the processing of multisource and multi-temporal data and DEMs by using field surveys, conceptual model, and analytical computation on a test area. The data acquired with two surveying techniques were analyzed and compared: Aerial Laser Scanning (ALS) and photogrammetry from stereo pairs of High-Resolution Satellite Images (HRSI). To assess the reliability of the DEMs produced from point clouds, the residuals between the point cloud and the interpolated filtered surface were identified and analyzed statistically. In addition to the contour maps, some feature maps such as slope, planar, and profile curvature maps were produced and analyzed. The frequency distribution of the slope and curvature values were compared with the diffusion, advection, and stream power model, revealing a good agreement with the past and present geomorphic processes acting on the different parts of the study area. Moreover, the integrated geomatics–geomorphic analysis of the outliers’ map showed a good correspondence (more than 75%) between the identified outliers and some specific geomorphological features, such as micro-landforms, which are significant for erosive and gravity-driven mechanisms. The different distribution of the above singularities by different data sources allowed us to attribute their spatial model to the temporal variation of the topography and, consequently, to the geomorphic changes, rather than to the different accuracy. For monitoring purposes and risk mitigation activities, the methodology adopted seems to meet the requirements to make a digital mapping of the coast analyzed, characterized by a rapid evolution of the surface, and can be extended to other stretches of coast with similar characteristics

Digital technology and geodetic infrastructures in Italian cartography

Traditional paper-based cartography was already being pushed aside decades ago by digital storing and pro-cessing of geographical information, meaning that information is now more easily accessible and can be transferred directly to the numerous software applications designed to manage all kinds of land-related tasks including planning, transportation, land management and emergency relief operations. It is now possible and economically viable to keep information constantly up to date with maps that describe a real-time situation rather than being narrowly confined to conditions on the ground at the moment of its creation. Software like the Geographic Information System (GIS) make it possible to capture, store, manipulate, ana-lyze, and manage visual representations of data in an extremely efficient manner, but it is precisely the geo-graphical nature of the information they work with that makes the support of digital cartography indispensa-ble, without which it would be impossible to position data spatially with the precision and reliability of a traditional map. Incorrect georeferencing of data severely diminishes its significance and usefulness. A map, whether it be traditional or digital, is closely linked to the geodetic system of which it is a part, and may in turn need to be updated in response to new technologies, specifically those which introduce new ways of acquiring geographical information in the field . It is therefore necessary to strictly define the meaning of the coordinates associated with each source, and the positioning of territorial information should be dependent on the geodetic and cartographical system. The current position of Italy on this subject is one of transition. The Italian authorities recently (2012) decid-ed to approve a new geodetic (and cartographical) system to facilitate harmonization with the geographical data of other European countries in accordance with the INSPIRE directive (INfrastructure for SPatial In-foRmation in Europe) , which Italy adopted through a legislative decree (DL 27 january 2012, n. 32), aimed at creating universal standards among European Union (EU) members in the interest of harmonization and information exchange. The current situation is an incentive for those authorities concerned with the man-agement of cartographical data to embark on a campaign of transformation and integration, and to overcome the complexities represented by an initial lack of homogeneity and by the excessive number of organizations responsible for cartography-related data: including ministries and cartographical institutes, regional govern-ments (who are the principal consumers of technical topographical and cartographical databases), local gov-ernments, and service providers