Estimation of Subsidence in Po Delta Area (Northern Italy) by Integration of GPS Data, High-Precision Leveling and Archival Orthometric Elevations

Abstract

Subsidence in a deformation area can be measured in various ways, examples being conventional high-precision leveling, differential InSAR and multi-temporal GPS surveys. Integration of methods can improve results, and is crucial to extract high-precision data. In particular, orthometric and ellipsoid elevations, surveyed at different moments in time, can be compared to yield information on vertical movements when geoid anomalies are known. However, a data checking procedure must be applied if archival orthometric elevations are used, because long-term measurements for many historical benchmarks may have been lost and/or replaced with other points, but at different elevations. This type of checking can be carried out over an area without gravimetric anomalies by modeling geoid undulations and vertical displacements in the time-span used for analysis, excluding points with anomalous values. This procedure was tested and applied in the Po Delta area (northern Italy), historically subject to high subsidence rates: the leveling benchmarks of 1983 were measured with the GPS technique in 2008. After checking of archival data and transformation from ellipsoid to orthometric elevations, comparisons of the same points and interpolations on the study area provided a subsidence map for the 1983-2008 period.

Land Subsidence Response to Different Land Use Types and Water Resource Utilization in Beijing-Tianjin-Hebei, China

“…More than 150 cities all over the world have endured land subsidence with rates up to tens of centimeters per year. Affected areas include China [1][2][3], Canada [4,5], Mexico [6][7][8], Italy [9][10][11][12][13], the United…”

Coastline evolution of the Po River Delta (Italy) by archival multi-temporal digital photogrammetry

“…For the others (1944, 1955, 1962, 1977, 1999 and 2014) the elevation values of the GCPs had to be corrected, due to land subsidence in the analysed period. A method based on archival subsidence values available in literature (Salvioni 1957;Zambon 1967;Caputo et al 1970Caputo et al , 1972Borgia et al 1982;Arca and Beretta 1985;Barbarella et al 1990;Baldi et al 2009;Cenni et al 2013;Fabris et al 2014) can be applied: for all GCPs, the elevation must be changed in multi-temporal analysis to report the values at the same time as the various photogrammetric flights. In addition, several GCPs were not visible for the oldest data due to the time which has elapsed since 2008, during which the territory has changed significantly.…”

“…Several methods can be used to study ground deformations such as global positioning systems (GPS or later GNSSglobal navigation satellite system), both continuous (CGPS) and differential (DGPS) (Bitelli et al 2000;Baldi et al 2009;Cenni et al 2013), space-borne observation techniques based on synthetic aperture radar (SAR), interferometry (InSAR, with differential InSAR -DInSAR and advanced differential A-DInSAR that allow to maximize the potential of this technique and permit time series analysis) (Bock et al 2012;Teatini et al 2012;Costantini et al 2017;Fiaschi et al 2018), satellite images (acquired with various kinds of sensors, with mono and/ or stereo ground coverage), classical topographic measurements and repeated geometric levelling on benchmarks (Barbarella et al 1990;Bondesan et al 1997;Fabris et al 2014;Hung et al 2018), light detection and ranging (LiDAR) with airborne laser scanning (ALS) approach (Fabris et al 2010;Marsella et al 2012) and aerial digital photogrammetry (Baldi et al 2005;Fabris and Pesci 2005;Baldi et al 2008aBaldi et al , 2008b. For limited areas, also unmanned aerial vehicle (UAV) (Mancini et al 2013) and terrestrial laser scanning (TLS) (Pesci et al 2007(Pesci et al , 2013 systems can successfully be used.…”

Geodetic monitoring and geotechnical analyses of subsidence induced settlements of historic structures

“…The phenomenon of subsidence in the plain as well as in the historic center of Modena has had a considerable effect in the past. [28,29] Several studies suggest a natural subsidence rate of the order of about 2.5 mm/year. These studies are based on topographic leveling campaigns carried out by the Italian Military Geographical Institute (IGM) between 1887 and 1889 and 1949-1950, a period in which it can be supposed that the Modena area has remained alien to subsidence induced by anthropogenic causes.…”