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| Titel |
Integration of reflectances and thermography imagery for transport infrastructures diagnostics |
| VerfasserIn |
S. Pignatti, A. Palombo, S. Pascucci, F. Santini |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250067336
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| Zusammenfassung |
| The integrated use of reflectances and thermography to study and diagnostic of transport
infrastructures has been applied on the Musumeci Bridge (Potenza, Italy) test site as a fast
and non-destructive tool in the framework of the Integrated System for Transport
Infrastructures surveillance and Monitoring by Electromagnetic Sensing (ISTIMES) project,
funded by the European Commission in the frame of a joint Call “ICT and Security” of the
Seventh Framework Programme, in order to extract appropriate information and make useful
decisions [1].
The applied hyperspectral imagery is primarily suited for the detection and
characterization of alterations and defects in the structures’ surface, whereas by means of
thermography it is possible to attain near real-time information about the internal structure
such as a bridge.
Hyperspectral data is able to discriminate materials on the basis of their different patterns
of wavelength-specific absorption; in fact, they are successfully used for identifying minerals
and rocks, as well as detecting surface materials properties [2]. For this study we used the
HySpex VNIR-1600 and the SWIR-320 hyperspectral scanners (see details in Table 1)
located beneath the Musmeci Bridge thus being able to acquire the structure. The
hyperspectral data processing has allowed to derive indication/parameters related
to the status of the structure surface, i.e. by means of the detection of the surface
weathering status of the iron (i.e. iron oxides such as limonite/goethite) used to reinforce
the cement structure and the occurring detachments of the cement covering the
iron. This assessment can be used to foresee more severe damages of the armed
concrete.
Concerning the rationale for using a high sensitivity Infrared camera in the MWIR range
(3.5-5 micron; see Table 1) for the Musumeci test site is based on the fact that the high
radiometric resolution of the thermal images time series allows analyzing the structure
homogeneity and the cohesion of the cement structure layer with the substrate. As favorable
environmental condition were satisfied: (a) the inner structure is thermally connected to the
external surface of the bridge structure and (b) the thermal gradient at the surface does not
depend on the atmospheric conditions (e.g., sun, rain, wind and so on), it was possible for the
Musumeci Bridge to detect with a good accuracy the underlying structure. More
specifically, the thermal series measuring sessions were executed during the night time
in order to record and understand the diurnal/nocturnal thermal behavior of the
structure according to the diurnal heating of the structure. Principal Components (PC)
analysis and the assessment of the parameters describing the thermal decay were used.
For this study the parameter that better describes the thermal decay of the bridge
corresponded to the angular coefficient of the curve better interpolating the temperature
decay ramp that for a limited interval of time could be approximated to a linear
decay.
The jointly use of the two non-destructive techniques applied for this project is
encouraged by the technical and operative characteristics of the observation systems at
disposal that are able to observe the variables, physical and optical parameters in near
real-time and connected to the transport infrastructures status. In particular, the hyperspectral
imagery processing results show that such methodology is suitable to identify reliable
parameters related to the structure surface by detecting anomalies and identifying the specific
signature of the material of interest. The thermal long time series processing, i.e. both the
PCA and decay coefficients images, has allowed to highlight the real inner structure of the
bridge.
From the proposed non-destructive monitoring approach on the Musumeci test site
experiences, we can conclude that the integrated use of the two sensing techniques is a valid
support for a rapid and low cost evaluation of the bridge structure and also with respect to the
rapidity of the sensing the output of this technology represents a powerful tool to
build the first informative level in the framework of an operative decision-support
system.
Table 1. Characteristics of sensors used for the study.
Spectral RegionSpectral ResolutionSpectral RangeIFOV Characteristics
Hyspex VNIR-1600 VIS-NIR 3.7 nm 0.4÷1.0μm 0.75 mrad160 bands (1600 pixels)
HySpex SWIR-320mSWIR 5.0 nm 1.3÷2.5μm 0.75 mrad240 bands (320 pixels)
FLIR SC7000 MWIR integrated 3.5÷5.0μm 1.20 mrad640 Ã 512 (5÷300 Ë C)
1 References
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Fornaro, G.; Gustafsson, M.; Hugenschimdt, J.; Kaspersen, P.; Kim, H.;
Lapenna, V.; Leggio, M.; Loperte, A.; Mazzetti, P.; Moroni, C.; Nativi, S.;
Nordebo, S.; Pacini, F.; Palombo, A.; Pascucci, S.; Perrone, A.; Pignatti, S.;
Ponzo, F.C.; Rizzo, E.; Soldovieri, F.; Taillade, F. Transport Infrastructure
Surveillance and Monitoring by Electromagnetic Sensing: The ISTIMES
Project. Sensors 2010, 10, 10620-10639.
Heiden, U., K. Segl, S. Roessner and H. Kaufmann. Determination of robust
spectral features for identification of urban surface materials in hyperspectral
remote sensing data. Remote Sensing of Environment, Vol. 111, pp. 537–552,
2007.
Acknowledgments
The research leading to these results has received funding from the European
Community’s Seventh Framework Programme (FP7/2007-2013) under Grant Agreement nË
225663. |
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