Evolution of the Geodetic Reference System in Italy: the RDN2

Renzo Maseroli, "Evoluzione del Sistema Geodetico di Riferimento in Italia: la RDN2 = Evolution of the Geodetic Reference System in Italy: the RDN2" in: Bollettino dell'Associazione Italiana di Cartografia, 153 (2015) pp.19-44Nel 2009 l'Italia ha aggiornato il Riferimento Geodetico europeo ETRS89 alla realizzazione ETRF2000 all'epoca 2008.0. Il nuovo trame è stato materializzato organizzando sul territorio un network costituito da 100 stazioni permanenti GNSS: la Rete Dinamica Nazionale (RDN). Al fine di verificare la stabilità dei siti RDN, l'IGM ha dato avvio, fin dal 2008, ad un continuo monitoraggio della rete, ottenuto attraverso ricalcoli periodici delle posizioni. Nel 2013 sono state elaborate le serie temporali dei primi 5 anni di attività, che hanno consentito una prima stima delle velocità sia assolute che interne alla placca. L’analisi dei risultati ha evidenziato siti con velocità intraplacca dell'ordine di 4 mm/anno, e conseguentemente la necessità di dover procedere a un aggiornamento delle posizioni, pena la perdita di efficienza del network. Inoltre, dal gennaio 2008 al 2013, il 20% circa delle stazioni RDN sono state dismesse o sono divenute inaffidabili, lasciando totalmente scoperte alcune zone del territorio nazionale. Al fine ripristinare l'integrità della rete e di mantenere una corretta geometria, l'IGM ha provveduto a reperire nuove stazioni GNSS da utilizzare in sostituzione dei siti dismessi o mal funzionanti, ed ha proceduto ad un ricalcolo complessivo dell'intero network che ha consentito l'aggiornamento delle posizioni delle stazioni al 2014.4, generando di fatto una RDN seconda versione (RDN2). Come previsto dall'art. 5 del Decreto 10 novembre 2011, l'IGM proporrà i suddetti aggiornamenti al Comitato per le regole tecniche sui dati territoriali delle pubbliche amministrazioni.In 2009, Italy has updated the European ETRS89 Geodetic Reference System implementing the realization ETRF2000 at epoch 2008.0. The new frame consists in a network of 100 permanent GNSS stations: the National Dynamic Network (RDN). In order to verify the stability of the RDN sites, the IGM started, since 2008, a continuous monitoring of the network, through periodic recalculations of the positions. In 2013 time series of the first 5 years of operation were processed; this computation allowed a first estimation of the absolute intraplate speed of the sites. The analysis showed sites with intraplate speed up to 4 mm / year, and consequently the need to proceed to an update of the positions in order to maintain the network efficiency. In addition, from January2008 to 2013, about 20% of the RDN stations have been discontinued or have become unreliable, leaving some areas of the country totally uncovered. In order to restore the integrity of the network and to maintain proper geometry, the IGM replaced the defaulting sites with new GNSS stations and recalculated the entire network updating the positions of the stations at epoch 2014.4; this process leads to the realization of RDN second version (RDN2). As per Art. 5 of the Decree of 10 November 2011, the IGM will propose these updates to the technical Committee for geospatial data

L’adozione del nuovo sistema di riferimento geodetico Italiano

Sulla Gazzetta Ufficiale n. 48 del 27 febbraio 2012 (supplemento ordinario n. 37) è stato pubblicato il DM con cui è stato adottato un nuovo sistema di riferimento denominato ETRF2000 (2008.0). I precedenti sistemi di riferimento, ancora in uso in Italia, sono il Roma40 (più conosciuto come Gauss-Boaga o MonteMario), l'ED50 (European Datum 1950 spesso chiamato semplicemente UTM) e l'ETRF89 (WGS84). Molti si chiederanno il perchè e quale sia la motivazione di fondo che ha portato lo Stato italiano ad adottare un quarto sistema di riferimento in meno di 100 anni. Adoption of a new geodetic reference system On  the  Official  Gazette  no.  48  of  27 February  2012 (ordinary  supplement no.  37)  was  published    the  Ministerial Decree which was adopted a new geodetic reference   system   called ETRF2000  (2008.0).  The previous  ref-erence systems, still in use in Italy, are the Roma40 (better known as Gauss-Boaga and often called MonteMario), the  ED50  (European  Datum  1950, often called  only  UTM)  and  ETRF89 (WGS84). Many will wonder why and what  the  underlying  motivation  that led  the  Italian government  to  take fourth  reference  system  in  less than 100 years

Ground Displacements Estimation through GNSS and Geometric Leveling: A Geological Interpretation of the 2016–2017 Seismic Sequence in Central Italy

Between August 2016 and January 2017, a very energetic seismic sequence induced substantial horizontal and vertical ground displacements in the Central Italian Apennines. After this event, the Italian Military Geographical Institute (IGM), owner and manager of the Italian geodetic networks, executed several topographic surveys in the earthquake area in order to update the coordinates of vertices belonging to the IGM95 geodetic network. The measurements began in the areas where the most significant deformation occurred: the localities of Amatrice and Accumoli, in the Rieti Province, and the area covering Norcia and Castelluccio, in the Province of Perugia, all the way to Visso (Province of Macerata). The activities described in this paper focused on the updated measurement of the IGM95 network points through GNSS and the restatement of extensive parts of the high precision geometric lines that were levelled until reaching stable zones. This unprecedented amount of data was used for a new geological interpretation of the seismic sequence, which confirms some of the previous hypotheses of the scientific community. In the analyzed territory, the latest estimate of the geodetic position points has allowed for an accurate determination of the east and the north and of the altitude components of the displacement induced by the earthquake through a comparison with the previous coordinates. The results confirm that the seismicity was induced by normal faults system activity. Still, they also indicate the possible influence of a significant regional thrust that conditioned the propagation of the seismicity in the area. The obtained maps of the displacement are coherent with other geodetic works and with a rupture propagation driven by the documented geotectonic structure

Orthometric correction and normal heights for Italian levelling network: a case study

Levelling increments must be corrected for gravity in order to get proper dynamic or orthometric heights. In Italy, most of the levelling lines have no associated gravity observations. Thus, only levelling increments are available, and corrections were computed only on a subset of the existing lines. However, gravity is densely observed, and thus, predictions of gravity along the levelling lines can be computed. This, in principle, would allow the estimation of corrections along the whole Italian levelling network. Furthermore, global model-derived gravity could be used for the same task (e.g. one could use the EGM2008 global geopotential model to get gravity estimates). To check for the reliability of these procedures, a test has been performed along levelling lines in the western Alps area. Both dynamic and orthometric corrections have been computed in order to finally get geopotential numbers, normal heights and orthometric heights from raw levelling increments. The results proved that reliable results can be obtained using the Italian gravity database, while predictions based on the EGM2008 model led to poorer estimates

Gravity corrections for the updated italian levelling network

The Italian official height system is defined through a high precision levelling network established and maintained by the Istituto Geografico Militare - IGM. During the last 20 years, IGM has performed levelling campaigns on almost the whole peninsular area of Italy with the aim of both densifying the existing network and updating the reference heights. This paper reports about the procedure applied to correct the levelling observations for the gravity effects and the assessment on the results. The needed gravity values were predicted from the Italian gravity dataset (IGD), and both from EGM2008 and XGM2019e high resolution global gravity models. A new formulation of the normal correction as well as the standard orthometric correction were applied. The IGD derived corrections proved to be effective by reducing the misclosure error of critical loops below the tolerance level. Gravity data derived from EGM2008 and XGM2019e proved to be too poor for the correction purposes, as it was also confirmed by a comparison against available observed data, with RMS of the differences, in Alpine ares, ranging between 50 and 100 mGal