Spectra of solar radiance reflected by leaves close to the Fraunhofer bands show the net contribution of chlorophyll fluorescence emission which adds to the reflected solar spectra. In a laboratory experiment, a low stray light, high resolution, 0.85 m double monochromator was used to filter radiation living leaves still attached to the plant in correspondence of the 687 nm and 760 nm O2 absorption bands. Reference spectra from a non fluorescent white reference were also acquired. Acquisition was performed by a Microchannel plate (MCP) intensified diode array with 512 elements. A fit of the spectral data outside the absorption lines allowed to retrieve the spectral base-line as a function of wavelength for the reference panel and the leaf. Reflectance functions were determined extending the Plascyck equation system to all the resolved lines of the oxygen absorption bands and using the base-lines for the continuum values. Fluorescence was deduced from the same equation system, using both the measured leaf and reference radiance spectra and the leaf reflectance fitting function.
The fluorescence lidar imaging technique turns particularly useful for the control of monuments. The investigated topics range from the detection of biodeteriogens to the characterization of stones and other masonry or restoration materials, such as protective treatments.
In addition, the fluorescence lidar imaging is a non-destructive technique offering the possibility of being carried out in situ without the use of scaffolding that, beside being costly, limits the access to the monument and its use.
This paper presents the main technical features of a new fluorescence imaging lidar system specifically developed for the diagnostics on the cultural heritage, whose operative conditions include outdoor and indoor environments, and the possibility of monitoring vaults and ceilings.
This fluorescence lidar prototype is mainly composed of a Q-switched, tripled frequency Nd:YAG laser (@355 nm), a 1 m focal length Newtonian telescope and a 300 mm focal length spectrometer coupled to an intensified, gated 512 x 512 CCD detector. Imaging is carried out via a scanning system realized with a computer controlled mirror. The lidar prototype includes also a target pointing system for referencing the acquired fluorescence images on the target.
Laser-induced fluorescence for remote imaging of historical monuments is an established technique, which in this
work has been used in measurement campaigns at the Coliseum and the Baptistery of San Giovanni in Laterano
in Rome, Italy. The results presented here are examples that show that biodeteriogens can be monitored and
that materials can be identified. Also, cleaned and soiled areas on the stone can be localized and differences
between soiling can be found, which may be useful in the sustainable conservation for mapping and evaluation.
LIDAR has to be considered as a key-tool for environmental remote sensing. A LIDAR measurement, based on the laser induced spectroscopy of a remote target, give the possibility of an accurate and fast monitoring of wide areas with good spatial and temporal resolution. LIDAR applications range from atmosphere to earth-surface remote sensing, offering the possibility of measuring significant environmental parameters, such as the concentration of different pollutants and of biological pigments. LIDAR sensors have been successfully employed from different mobile platforms, including van, ship, helicopter and aeroplane.
This paper illustrates the results of an experiment carried out using a fluorescence imaging lidar system with an Optical Parametric Oscillator (OPO) system as the excitation source. Fluorescence spectra of various samples of limestones, sandstones and mortars typically used in the building of historical monuments were investigated exciting at five different wavelengths in the UV region. The spectra were analyzed to produce thematic maps by using multivariate analysis. Besides giving the possibility to identify the optimal excitation wavelength for each specific lithotype or material, the experiment offers prospects for an improved method for the characterization of different materials based on a combined multivariate analysis of fluorescence spectra obtained at different excitation wavelengths.
The Laser Induced Fluorescence (LIF) technique has been widely employed for the study and the monitoring of the phytoplanktonic population in the marine environment. Herein a method for the characterization of different phytoplanktonic species by means of a high spectral resolution lidar fluorosensor is presented. The method is based on the detection of the changes in the peak position of the fluorescence of the chlorophyll a that is contained in all phytoplanktonic species. These changes are probably due to the proteic compounds that are present together with the chlorophyll in the thylakoid membranes within the chloroplasts and that vary with the phytoplanktonic species. The main advantage is that this method does not require the presence of characteristic fluorescence features of other light harvesting pigments, such as carotenoids or phycobilines, so that it can be used also with species where only chlorophyll fluorescence is present. Moreover, the light harvesting pigments usually show a weak fluorescence because of the strong resonant coupling between them.
Fluorescence lidar is a well known instrument that is mainly employed for the remote sensing of the Earth's surface. In recent years, IROE, in collaboration with other Italian and foreign institutions, carried out the first experiments on remote sensing of historical buildings using fluorescence lidar. The main part of these experiments deals with the remote monitoring of biodeteriogens and the lithological characteristics of the building materials. This paper describes the results of the field experiment carried out at the Parma Cathedral and Baptistery in September 2000. Two systems, the tripled Nd:YAG lidar of the Lund Institute of Technology and the XeCl lidar of the CNR-IROE, operated for one week, in order to test the possible applications of both fluorescence point measurement and fluorescence thematic imaging in the remote non-destructive monitoring of buildings. Apart from confirming the possibility of detecting biodeteriogens, for the first time in our knowledge the processing of the fluorescence data made possible the detection of restorations and the distinction between pigments having the same color.
The monitoring of organic matter, suspended or dissolved in the water column, is relevant for the study of the aquatic environment. Actually, the Dissolved Organic Matter (DOM) represents a major reservoir of reactive carbon in the global carbon cycle, thus influencing significantly the marine ecosystem. Due to the strong absorption in the near ultraviolet, DOM reduces considerably the extinction path of solar light in the water column, affecting phytoplankton population and its vertical distribution. The measurement of the DOM absorption coefficient has to be regarded as a good parameter for the monitoring of water quality. This paper deals with the measurements carried out during the oceanographic campaign 'Marine Fronts,' which took place in the Western Mediterranean Sea and Atlantic Ocean from July 14 to August 5, 1998. In this measurement campaign, a high spectral resolution fluorescence lidar (FLIDAR) was installed on the rear-deck of the O/V 'Urania,' acquiring remote fluorescence spectra both in ship motion and in stations. A particular attention was devoted to the monitoring of DOM distribution in the different water masses in marine frontal areas. The lidar data were compared and integrated with SST satellite data and biological samplings. The results show that FLIDAR data agree with satellite imagery, particularly for marine front detection. The comparison with water sample data gave indications for retrieving the DOM absorption coefficient directly from fluorescence remote spectra. In addition, a protein like fluorescence band was detected in the measurements carried out on total suspended matter filtered from the water samplings.
This paper reports on the first lidar imaging experiments carried out on a historical monument. The measurements were carried out by scanning the northern facade of the Lund cathedral from a distance of at least 60 m with a mobile fluorescence lidar. Two different arrangements were used for the receiver: an optical multi-spectral analyzer or two photomultipliers equipped with interference filters. Depending on the wavelength the fluorescence images allow the mapping of biodirection colonization or of the different stony materials. To our knowledge these were the first images of a historical building detected by a fluorescence lidar.
The PRISMA is a research project, sponsored by the Italian Ministry for University and Scientific Research, devoted to the study of the Adriatic Sea. Within this project, the general goal of the IROE has been the development of a measurement procedure for the detection of marine fronts which integrates the NOAA-AVHRR imagery and the fluorescence lidar data. The paper reports the activity performed during the different measurement campaigns and discusses the results obtained during the first winter campaign carried out in February 1997. A good agreement was found between the front position as detected on the AVHRR thermal images and the position detected by the fluorescence lidar on the base of the change in chlorophyll and DOM concentration as well as in the change of the water Raman signal.
The total attenuation coefficient is a significant parameter of the water column being strictly related to the light penetration depth and to the quantity of suspended and dissolved substances. This parameter is measured in situ by optical instruments while its remote measurement can be achieved by lidars. The lidar measurement of the total attenuation coefficient is based on the Raman scattering due to the OH stretching of water molecule. This paper discusses the analytical base of the measurement.
A joint IROE-CNR, NASA/GSFC, and USDA/ARS measurement campaign was conducted in Italy for a three week period in July, 1997. The campaign was split into two parts: the first part for aquatic vegetation studies and the second part for terrestrial vegetation studies. The main objective of the campaign was to study optical properties of intact plant material as it relates to photosynthetic activity of living vegetation. The aquatic studies were carried out at an aquarium-laboratory in the seashore city of Livorno on the West coast of Italy. The investigations involved an important sea grass species that is native to the Mediterranean Sea. The terrestrial studies were carried out Northeast of the Town of St. Stefano di Cadore (Belluno), Italy. Measurements were taken in a wooded site at an Italian Department of Forestry Station on species of natural alpine vegetation. Instrumentation available for the studies were the Italian Fluorescence Light Detection And Ranging (FLIDAR) System, the NASA/USDA Fluorescence Imaging System (FIS), the Perkin Elmer Spectrofluorometer and LI-COR 6400 infrared gas exchange analyzer for photosynthesis measurements. Preliminary evaluations, analysis, and summaries were made by personnel from both Italian and United Sates groups on data collected during the measurement campaign. The joint Italian/American data collection effort with Aquatic and Terrestrial Optical Measurements produced a range of data for characterizing the relationships between fluorescence and the photosynthetic potentials of vegetative scenes.
Aquatic vegetation studies were carried out from Tuesday July 15th, 1997 to Tuesday July 22, 1997 in a sea-side aquarium- laboratory in the city of Livorno on the Tyrrhenian Sea. The investigations involved an important sea grass species Posidonia oceanica that is the main higher aquatic vegetation found in the Mediterranean Sea. Fluorescence measurements were acquired on the aquatic plants treated with different levels of Mercury and Cadmium heavy metal contamination. The measurements included steady state fluorescence and fluorescence induction kinetics, pigment extraction, and photosynthetic gas exchange rates. Fluorescence instrumentation used for the studies included the high spectral resolution fluorescence lidar System (FLIDAR$CPY), the NASA/USDA Fluorescence Imaging System (FIS), and Perkin Elmer Spectrofluorometer. Fluorescence responses showed a significant variations within the leaf as a function location from the base. Heavy metal treatments resulted in distinguishable differences in fluorescence responses.
Terrestrial vegetation studies were carried out in the Italian Northeastern Alps in Val Visdende. The measurement site was 15 Kilometers Northeast of the town of St. Stefano di Calore (Belluno), Italy. Measurements were acquired on a wooded site at the Italian Department of Forestry Station on species native to the Italian Alps. The species included spruce (Picea abies) and alder (Alnus incana) trees. Characterization was also made of the fluorescence responses of several under-story species such as Dactylorhiza fuchsii of the Orchidaceae family, Caltha palustris and Ranunculus ficaria of the Ranuncolcee family, and Trifolium pratense and Trifolium repens of the Leguminosae family. Terrestrial vegetation monitoring was conducted with the Italian FLIDAR remote sensing instrument mounted in a mobile van, the NASA/USDA Fluorescence Imaging System (FIS), and the Spectron SE-590 for optical properties. Photosynthetic CO2 gas exchange rates we made with LI-COR 6400 infrared gas analyzer. Pigments from the samples were extracted and analyzed with a Perkin Elmer Lamda 7 Spectrometer to determine pigment concentrations. Fluorescence responses were collected from vegetation samples grown under different ambient light regimes of sun-lit versus shaded. The vegetation showed different fluorescence characteristics. A fluorescence algorithm, (F740/F680)/F550, and rate of photosynthesis showed a strong linear relationship.
Stone surface monitoring of historical buildings is of interest in the planning of restoration work, both for assessing biodeteriogen growth and for detecting the spectroscopic features of the surface itself. Laser-induced fluorescence (LIF) analysis yields strong signals in the near IR region due to algal depositions while signals through the visible region are useful for the characterization of the stone materials. This paper reports on the first experiments carried out in the framework of a joint project of LTH and IROE-CNR aimed at the fluorescence imaging of historical buildings. We have used a fiber-optical fluorosensor for performing point measurements, and a mobile fluorescence imaging lidar system for remote measurements at a typical distance of 60 m.
The Venice lagoon collects different realities, such as the historical Venice town, the main industries of Marghera, and a large traffic harbor. The water exchange is mainly provided by tidal movements. In such an environment, a continuous monitoring is necessary to avoid water eutrophication and pollution phenomena like sudden algal blooms and anoxia. In the framework of a national project some measurement campaigns were carried out during recent years to point out the usefulness of fluorescence lidar also in this particular marine environment. A high spectral resolution fluorescence lidar operated from different platforms along the Venice lagoon with simultaneous traditional monitoring and sampling. The experiments demonstrated the advantages of lidar remote sensing in the monitoring of the lagoon water quality. The results are comparable to conventional field measurements with the advantage that, in measurements scheduled over an extended time, the need of maintenance is not costly and tedious as for in situ measurements.
The SALE experiment was carried out in September 1994 in waters of the Southern Tyrrhenian Sea and in Sicilian coastal waters. The aim of the experiments was the test of lidar potential in the simultaneous measurement of atmospheric and marine parameters in this particular environment. A DIAL and fluorescence lidar were successfully employed for the monitoring of volcanic emissions and marine parameters, respectively. the paper describes and discusses the main results of this experiment.
This paper deals with laboratory and filed experiments carried out in the last few years by the authors for the detection of underwater temperature by Raman scattering. Laboratory experiments have been aimed at the implementation of a procedure to be transferred to the remote sensing application, so that only relative parameters have been considered. Field experiments have been carried out during oceanographic campaigns in the Tyrrhenian Sea with a high spectral resolution lidar. The results outline the usefulness of high spectral resolution lidars for the detection of underwater temperature, opening the possibility of applying more refined elaboration procedures for the extraction of underwater temperature.
Lidars have already been used as an effective tool for the monitoring of marine environment and vegetation. In this paper the data relative to the first fluorescence lidar experiments on the facades of historical buildings are presented and discussed. The lidar fluorescence spectra presented in this paper were detected with a high spectral resolution fluorescence lidar on the Baptistery of Parma and mainly refer to the coatings of Ammonitico Rosso Veronese, a calcareous stone widely employed as decorative material for its color and typical texture. These data were also compared to the lidar spectra of samples coming from different sites situated in the extraction areas historically known from the archives and from sites in an area exploited only quite recently. The results constitute a first step towards a completely non destructive spectral analysis directly on the surfaces of the historical buildings.
Fluorescence techniques have been extensively used for the detection of photoautotrophic organisms. In particular, fluorescence lidars have been successfully employed for the detection and identification of phytoplankton in sea water and, more recently, have been regarded as powerful tools for vegetation monitoring, especially as for the evaluation of forest decline. In this paper the fluorescence lidar technique is proposed as a new tool for the remote monitoring of photoautotrophic biodeteriogens on surfaces of historical monuments. The use of fluorescence lidars can remotely detect photoautotrophic organisms on monuments and, with a suitable spectral resolution, identify the pigments contained into. The advantages of the fluorescence lidar technique with respect to the traditional methods are manifold and can lead to a fast, extensive control of the stony cultural heritage at low cost. Laboratory and lidar experiments were carried out on different stony materials inoculated with microalgal and cyanobacterial species at different cell concentrations to investigate the potentialities of this technique. The experimental results presented in this paper include the remote detection of biodeteriogens on stony materials at a previsual growth stage by means of a fluorescence lidar and the identification of the fluorescence features of different pigments.
The FLIDAR, built at IROE-CNR in Florence, was the first of a new generation of sensors operating with high spectral resolution both as fluorescence lidar and passive spectrometer. This research includes the sensor development and the study of a suitable data processing for an extensive monitoring of the marine environment. As a result, both the laboratory and field experiments allowed the monitoring of: (1) water column temperature, by the water-Raman spectral shape; (2) oil pollution (oil class identification and thickness), by both the oil fluorescence spectral features and the water-Raman signal intensity; (3) phytoplankton and phytobenthos (identification and stress), by their fluorescence spectral signatures and their spectral behavior; (4) mucillagine, its observation has been carried out directly in the field, addressing a method for its detection. Finally, the FLIDAR has been operating since 1991 from different platforms, such as ship, helicopter, and airplane.
In recent years the improvement of the spectral and radiometric performances of optical detection systems has allowed the development of high spectral resolution remote sensors. Both passive and active sensors have taken advantage of this technological improvement and, as to the active ones, also from the contemporary development of new laser sources. At present, passive hyperspectral scanners with the simultaneous detection of more than 100 spectral images for each frame and fluorescence lidars with some hundreds of channels or with imaging capability are available. These instruments can now perform a remote spectroscopy of environmental targets with a spectral resolution similar to the laboratory one. However, in order to reduce the amount of data, it is necessary to exploit all the possible synergisms between active and passive optical sensors. This paper deals with the evaluation, the advantages and disadvantages of different solutions for the integration of active and passive sensors and formulates some hypothesis for sensor development and their use from flying platforms.
Fluorescence lidar is an interesting tool for the control of vegetation status, monitoring stresses also at an early, previsual stage. However, a complete physiological interpretation of the fluorescence spectra and their variations related to the plant stresses is still missing. A research project dealing with both instrument development and data interpretation has been carried out at our institutes in the framework of the national programs IPRA and RAISA (technology for agriculture) and of the EUREKA/LASFLEUR (EU380) project. Laboratory experiments dealt with the interpretation of the physiological significance of blue-green and red vegetation fluorescence and with the analysis of the influence of stresses on the spectral behavior. The experiments were carried out both in spectroscopy laboratory, in greenhouses under controlled conditions (i.e., photosynthetic photon flux density, net photosynthesis, and different stresses) and, finally, in the field from ground based and flying platforms using the fluorescence lidar FLIDAR3.
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