For all the European Countries, the rail network represents a key critical infrastructure, deserving protection
in view of its continuous structure spread over the whole territory, of the high number of European citizens
using it for personal and professional reasons, and of the large volume of freight moving through it.
Railway infrastructures monitoring with COSMO/SkyMed imagery
and multi-temporal SAR interferometry (ID: 1464682)
M. T. Chiaradia1, R. Nutricato1,2, D. O. Nitti1,2, F. Bovenga3, L. Guerriero1,2
1 Politecnico di Bari, Italy, 2 Geophysical Applications Processing – GAP srl, Bari, Italy, 3 National Research Council of Italy, CNR-ISSIA, Bari, Italy
[1] F. Bovenga et al., “SPINUA: A flexible processing chain for ERS/ENVISAT long term interferometry,” in Proc. ERS-ENVISAT Symp., Salzburg, Austria, 2004.
[2] F. Bovenga et al., “Application of multi-temporal differential interferometry to slope instability detection in Urban/Peri-urban areas,” Eng. Geol., vol. 88, no. 3/4, pp. 218–239, Dec. 2006.
[3] F. Bovenga et al., “Using COSMO/SkyMed X-band and ENVISAT C-band SAR interferometry for landslides analysis”, Remote Sensing of Environment, Volume 119, 16 April 2012, Pages 272-285.
[4] D. Calcaterra et al.,"Weathering-related Slope Instabilities of The Calabrian Arc (italy)". EGS XXVII General Assembly, Nice, 21-26 April 2002, abstract #2862.
[5] L. Cascini et al., “Advanced low- and full-resolution DInSAR map generation for slow-moving landslide analysis at different scales”. Engineering Geology, 112(1–4), 29–42, 2010.
[6] M. T. Chiaradia et al., “On the COSMO-SkyMed Exploitation for InSAR DEM Generation". AGU Fall Meeting, San Francisco, California, USA, 5-9 Dec. 2011, abstract #EP41A-0574.
[7] C. Colesanti et al. "Monitoring landslides and tectonic motions with the Permanent Scatterers Technique". Engineering Geology, 68(1), 3-14, 2003.
[8] C. Del Ventisette et al., "Using ground based radar interferometry during emergency: the case of the A3 motorway (Calabria Region, Italy) threatened by a landslide". Nat. Haz. Earth Syst. Sci., 2011.
[9] A. Ferretti et al., “Permanent scatterers in SAR Interferometry”. IEEE Transactions on Geoscience and Remote Sensing, 39, pp. 8–20, 2001.
[10] R. F. Hanssen, “Radar Interferometry: Data Interpretation and Error Analysis”. Dordrecht: Kluwer Academic Publishers, pp. 308, 2001.
[11] G. Iovine et al., "Emergency management of landslide risk during Autumn-Winter 2008/2009 in Calabria (Italy). The example of San Benedetto Ullano". 18th World IMACS / MODSIM Congress, 2009.
[12] G. Ketelaar. Monitoring surface deformation induced by hydrocarbon production using satellite radar interferometry. PhD Thesis, 2008.
[13] D. Reale et al., "Postseismic Deformation Monitoring With The COSMO/SKYMED Constellation". IEEE Geoscience Remote Sensing Letters, 2011.
[14] The IIFFI Project (Italian Landslide Inventory): http://www.sinanet.apat.it/progettoiffi
[15] National Geoportal (NG) of the Extraordinary Plan of Environmental Remote Sensing (EPRS-E): http://www.pcn.minambiente.it/GN/
Acknowledgements
CSK images provided by ASI (Agenzia Spaziale Italiana) in the framework
of the project “Landslide Monitoring and Mapping System - CAR-SLIDE”
(PON 01 00536). Optical images provided by GoogleEarth and
GoogleStreet. The authors would like to thank dr. J. Wasowski (CNR-IRPI,
Bari, Italy) for helpful comments on the achieved results.
Fig.3
0 2 km 4 km
Contacts
For further details please contact:
Multi-temporal Interferometric Analysis
SPINUA (Stable Point INterferometry over Un-urbanised Areas)
is a Persistent Scatterers (PS) interferometric algorithm for multi-
temporal Differential SAR Interferometric analysis. The processing
chain is the result of a joint effort of the Remote Sensing Group of
the Department of Physics at Politecnico di Bari and the ISSIA-CNR
institute of Bari. SPINUA has been developed with the aim of
detection and monitoring of coherent PS targets in non- or scarcely-
urbanized areas [1,2]. The processing chain has been further
updated in order to deal properly with X-band data from both CSK
and TerraSAR-X.
COMMENTS – The achieved results indicate that multitemporal SAR interferometric techniques may represent a valid and powerful tool for a
wide-scale constant monitoring of ground deformations occurring along railway infrastructures as well as surrounding areas affected by hydro-
geological instabilities. The X-band COSMO/SkyMed constellation represents an important added value since, thanks to the higher spatial and
temporal resolution, it allows to discriminate deformation regimes, such as structural instabilities, shallow and deep mass displacements [12].
SAR interferometry is the coherent combination of two (or more) SLC
images of the same area taken from slightly different directions:
COSMO SkyMed (CSK) constellation is an Italian Space Agency (ASI) mission made of 4 satellites able to
acquire SAR images in several imaging modes. CSK SAR sensor works in X-band providing spatial resolution
one order of magnitude better than the previous available satellite SAR data, as well as short revisit time (up to
8 hours for the full constellation). Recent scientific works have shown the advantages of using CSK in the monitoring of terrain deformations
caused by landslides, earthquakes, etc [3,13]. On the other hand, thanks to the high spatial resolution, CSK appears to be very promising in
monitoring man-made structures, such as buildings, bridges, railways and highways, thus enabling new potential applications. The multi-
beam capability (off-nadir look angle may be selected from 16° to 52°), as well as the right/left look side, gives us the ability to improve their
visibility along the line-of-sight (LOS): this depends indeed on the local orientation of the area, described by the aspect and slope
(inclination), with respect to the LOS. Starting from orbit information and from an available DEM, a visibility map can be derived [5] allowing
a preliminary inspection of the territory with the aim of searching areas suitable to InSAR monitoring, on one side, and selecting the best
available geometry (ascending or descending passes) on the other side.
Barritteri Reggio Calabria
ABSTRACT – The present work investigates the potentialities of the COSMO/SkyMed (CSK) constellation for railway infrastructures
monitoring through multitemporal SAR interferometric analyses with particular attention devoted to the impact of the improved spatial
resolution with respect to the previous SAR sensors.
A dataset of 57 right-looking CSK stripmap
Single-Look-Complex (SLC) images was
ordered: the full frame entirely covers the
area of interest, i.e. the stretch of the
Tyrrhenian railway line between Palmi and
Reggio Calabria (Region: Calabria, Italy), as
shown in Fig.1. The images were acquired
by the first two sensors of the constellation
between October 2009 and April 2012
(mean rate: one acquisition every 16 days),
along ascending pass in HH polarization at
a look angle of 29 deg (beam H4-03).
Range Chirp and Doppler Bandwidths are
~120 Mhz and 2.55 kHz, respectively,
leading to a ground resolution of 3x3 m2.
Fig.2 Fig.1
CSK Dataset
Introduction
The present study has been carried out in the framework of a scientific project named CAR-SLIDE (Mapping
and monitoring system for landslides forecast), funded by the Italian Ministry of Education, Universities and
Research (MIUR), aimed at producing a diagnostic system, capable to foresee and monitor landslide events
along railway networks by integrating in situ data, detected from on board sophisticated innovative measuring
systems, with Earth Observation (EO) techniques.
Railway system traverses a wide variety of terrains and encounters a range of geo-technical conditions. The interaction of these factors
together with climatic, and seismic forcing, may produce ground instabilities that impact on the safety and efficiency of rail operations.
In such context, a particular interest is directed to the development of technologies regarding both the prevention of mishaps of
infrastructures, due to natural disasters and/or to terrorist attacks, and the fast recovery of their normal working conditions after the
occurrence of accidents (disaster managing). Both these issues are of strategic interest for EU Countries, and in particular for Italy, since,
more than other countries, it is characterized by a geo-morphological and hydro-geological structure complexity that increases the risk of
natural catastrophes due to landslides, overflowings and floods.
Particular importance is attached to the use of advanced SAR interferometry, thanks to their all-
weather, day-night capability to detect and measure with sub-centimeter accuracy ground surface
displacements that, in such context, can occur before a landslide event or after that movements [7].
Special attention is directed to the use of SAR images acquired by CSK constellation capable to
achieve very high spatial resolution and very short revisit and response time [3,13].
In this context, a stack of 57 CSK stripmap images has been acquired, covering the Calabria's Tyrrhenian
coast, between the towns of Palmi and Reggio Calabria. The imaged area is of strategic importance since
The two towns are connected by a stretch of the Tyrrhenian railway line, a fundamental line (as classified
by RFI, the Italian Rail Network) belonging to the TEN-T network, i.e. the trans-european transport network
defined since early '90 by the European Commission. Moreover, Calabria region is a challenging area where carrying on an analysis on
weathering-related slope movements [4]. In Calabria, on 2009 the geo-hydrological crisis was so severe that the Italian Government had to
declare the state of emergency [8,11]. This work concerns the processing of the CSK dataset through multi-temporal InSAR techniques.
Displacement maps derived on the area of interest are presented and commented with particular attention to the potential impact that such
EO-based product can have on the railway networks monitoring, threatened by local failures as well as landslide phenomena [8].
Fig.4a
Fig.4b
Multi-temporal interferometric techniques have been developed with
the aim of tackling the effects of critical error sources, such as that
associated with the interaction between the microwave signal and the
atmosphere [10], that may limit the accuracy of topography estimation
and detection of small movements. By processing stacks of SAR
images, several differential interferograms are generated and properly
combined to allow identifying and monitoring targets on the ground that
remain coherent to a sufficient degree through time [9]. For these
targets it is possible to provide time series of accurate displacements,
as well as very precise topographic corrections to the reference
topography thus allowing also precise geographic localization even at
the highest (full) sensor resolution.
Here we report the results obtained by processing through SPINUA
algorithm the CSK stripmap dataset in Fig.2. Figure 3 shows the
displacement rate map for the entire investigated area, delimited by the
gray-shaded area. The density of the measurable coherent targets
depends on the ground coverage, and it is maximum (even > 40K
PS/km2) over urban areas thanks to the abundance of artificial
structures with coherent backscattering. It drops abruptly, instead, over
vegetated areas (because of the poor penetration depth of the radar
signal, especially in X-band) or along slopes affected by layover and
shadow. These results are in line to those obtained on other sites [6].
Refe
ren
ces
Normal Baselines span around 1.8 km, as shown by the spatial and temporal baseline distribution of Fig. 2.
ErrATMMOV
INT hr
B
sin
4
0
Topography Atmospheric
artifacts Movement
Processing errors
(noise, orbital inaccuracy)
Figure 4 refers to the stretch of the
TEN-T railway line between
Bagnara Calabra and Favazzina,
two small towns along the
Calabria’s Thyrrenian coast. Fig.4a
refers to the displacement rate
map, while the refined topographic
information (w.r.t. a reference
SRTM 90-m DEM) is shown in Fig.
4b. The entire stretch is densely
covered by PS, thus allowing a
constant and uniform monitoring.
Further examples are shown in the
insets below (Figures 5÷9).
Due to its complex orography and litography [4],
many case studies of infrastructures threatened
by landslides have been documented in the
Calabria Region [8]. Fig.7 shows moving PS over
all the extension of the “Giambarelli” viaduct (A3
highway), close to Barritteri town, due to ground
instabilities also reported in the IFFI web
catalogue [14]. Our results are in line with low-
resolution ascending ASAR C-band velocity
maps provided by [15] for the period 2002-2009.
A stretch of the TEN-T Calabrian
railway fundamental line between
Scilla and Favazzina towns, along the
Thyrrenian shoreline. The measured
linear PS density along the railway
line is close to the full SAR sensor
resolution (3m) for all tracks in
visibility (no tunnels) and not affected
by strong SAR distortions due to the
surrounding slopes.
The inset on the left shows
many moving coherent
scatterers (such as those
labeled PS_A and PS_B in
Fig.5b/c) along the old
elevated railway due to local
instabilities, while the
underlying breakwater seems
to be stable. Measured ground
mean velocities are close to
7÷8 mm/yr. Local inspections
are ongoing in the area.
Scilla-Favazzina Fig.5a
Fig.5b
Fig.7 Figures 8 and 9 refer to the Reggio Calabria urban area.
These test sites have been selected as further example of
the high density of coherent scatterers achievable over
man-made structures (buildings, railway lines, highways
and airports) with high resolution X-band SAR satellite
sensors, thus encouraging new potential applications, as
intra-building deformation mapping.
Fig.4
Fig.5
Fig.7
Fig.8
Fig.6
Fig.9
Fig.9b
Fig.9a Fig.8
“Tito Menniti”
Airport (REG)
R.C. Central
Railway Station
Railway Station
R.C. S.Gregorio
IFFI
Archi Another example of ground
instabilities affecting the
Thyrrenian railway line.
Local inspections are
ongoing in the area.
Fig.6
Fig.5c
PS_A PS_B
PS_B PS_A