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- Lognoli, D, et al.
(författare)
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Fluorescence lidar imaging of the cathedral and baptistery of Parma
- 2003
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Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171. ; 76:4, s. 457-465
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Tidskriftsartikel (refereegranskat)abstract
- Extensive fluorescence multispectral imaging of the cathedral and baptistery of Parma, Italy, is reported and discussed. In particular, the first fluorescence imaging data from protection-treated stony materials were recorded. Fluorescence spectra were taken with a mobile lidar system scanning the monument surfaces with a frequency-tripled Nd:YAG laser beam from a distance of about 80 m. For each pixel of the area investigated, a high-spectral-resolution spectrum in the full visible range was acquired. The principal-component analysis technique was used to obtain thematic maps that outlined areas subject to protective treatment and biological growth, and other features, such as different types of stones and decoration pigments.
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- Weibring, Petter, et al.
(författare)
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Fluorescence lidar imaging of historical monuments
- 2001
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Ingår i: Applied Optics. - 2155-3165. ; 40:33, s. 6111-6120
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Tidskriftsartikel (refereegranskat)abstract
- What is believed to be the first fluorescence imaging of the facades of a historical building, which was accomplished with a scanning fluorescence lidar system, is reported. The mobile system was placed at a distance of similar to 60 m from the medieval Lund Cathedral (Sweden), and a 355-nm pulsed laser beam was swept over the stone facades row by row while spectrally resolved fluorescence signals of each measurement point were recorded. By multispectral image processing, either by formation of simple spectral-band ratios or by use of multivariate techniques, areas with different spectral signatures were classified. In particular, biological growth was observed and different stone types were distinguished. The technique can yield data for use in facade status assessment and restoration planning. (C) 2001 Optical Society of America.
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- Weibring, Petter, et al.
(författare)
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Monitoring of volcanic sulphur dioxide emissions using differential absorption lidar (DIAL), differential optical absorption spectroscopy (DOAS), and correlation spectroscopy (COSPEC)
- 1998
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Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171. ; 67:4, s. 419-426
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Tidskriftsartikel (refereegranskat)abstract
- The total fluxes of sulphur dioxide from the Italian volcanoes Etna, Stromboli, and Vulcano were studied using optical remote sensing techniques in three shipborne field experiments (1992, 1994, and 1997). The main purpose of the experiments was to compare active (laser) techniques with passive monitoring. Differential absorption lidar (DIAL) measurements were implemented by placing the Swedish mobile lidar system on board the Italian research vessel Urania, sailing under the volcanic plumes. Simultaneously, the passive differential optical absorption spectroscopy (DOAS) technique was used for assessing the total overhead gas burden. Finally, correlation spectroscopy (COSPEC) was also implemented in one of the campaigns. Differences in integrated gas column assessment are expected and observed, mostly connected to complex scattering conditions influencing the passive measurements. Since such measurements are much employed in routine volcanic monitoring it is of great interest to model and provide corrections to the raw data obtained. Lidar measurements proved to be quite useful for this purpose. By combining the integrated gas concentration over the plume cross section with wind velocity data, SO2 fluxes of the order of 1000, 100, and 10 tonnes/day were measured for Mt. Etna, Stromboli, and Vulcano, respectively.
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- Weibring, Petter, et al.
(författare)
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Optical monitoring of volcanic sulphur dioxide emissions - comparison between four different remote-sensing spectroscopic techniques
- 2002
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Ingår i: Optics and Lasers in Engineering. - 0143-8166. ; 37:2-3, s. 267-284
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Tidskriftsartikel (refereegranskat)abstract
- The emissions of sulphur dioxide from the Italian volcanoes Mt. Etna and Stromboli were studied in ship-borne underpasses of their plumes. Four different optical spectroscopy techniques were used and inter-compared. All techniques utilise the absorption signature of the gas in the wavelength region of around 300 nm. A differential absorption lidar was employed in active gas concentration assessment. In parallel, a differential optical absorption spectroscopy system (DOAS) provided spectrally resolved absorption spectra, In one configuration the DOAS used a vertically looking telescope and the absorption of the skylight was studied, while a different DOAS implementation utilised the sun disc as the light source in slant-angle, long-path absorption measurements. Parallel measurements with the customary correlation spectroscopy method were also performed. Path length Monte Carlo simulations of the down-welling radiation through the volcanic plume at different sun altitude and azimuth angles have been performed taking into account also the effects of other geometric parameters as the plume height and extension. The results are discussed with special emphasis on systematic effects due to scattering.
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