Giovanna Cecchi

Fluorescence lidar imaging of historical monuments

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 ~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.

Remote sensing of chlorophyll a fluorescence of vegetation canopies: 1. Near and far field measurement techniques

Abstract This article presents instruments and techniques, used in several vegetation monitoring experiments. Simultaneous monitoring was performed with different approaches, including fluorescence lidar and passive remote sensing, leaf level reflectance, and laser fluorimetry, and compared with physiological measurements. Most of the instrumentation described was designed and built for this application. Experiments were carried out in the laboratory and in the field, to investigate the relationship between chlorophyll fluorescence spectra and plant ecophysiology. Remote sensing, spectroscopy, and ecophysiology data were then collected by an intensive research team, joining different experiences and working in national and international projects.

Remote sensing of chlorophyll a fluorescence of vegetation canopies: 2. Physiological significance of fluorescence signal in response to environmental stresses☆

Abstract Measurements of laser-induced chlorophyll fluorescence of living leaves were compared to ecophysiological parameters, both in near and far field conditions. Near field measurements were carried out with a two-wavelength portable fluorometer, both in the laboratory and in the field. Results show significant changes of the 690 nm and 730 nm chlorophyll fluorescence bands in different environmental conditions. Water stress and carboxylation limitations also affect the fluorescence spectra. Far field measurements from a ground-operated fluorescence LIDAR system confirm those results. The F690 / F730 fluorescence ratio is then demonstrated as a good index for vegetation remote sensing.

The F685/F730 Chlorophyll Fluorescence Ratio as Indicator of Chilling Stress in Plants

Summary The response of chlorophyll fluorescence to chilling temperatures was evaluated by two different experiments. In the first, the F685/F730 and the F v /F m chlorophyll fluorescence ratios were measured in Phaseolus vulgaris L., cv. Mondragone plants under chilling stress at 4 °C and moderate light (100 μmol m -2 s -1 ) up to 72 hours. F v /F m decreased linearly with chilling time indicating a photoinhibitory effect (no change was observed in the dark under the same conditions). F685/F730 underwent a rapid exponential decay followed by a linear slow decline. In a second experiment, the F685/F730 ratio, the total chlorophyll fluorescence, F685 + F730, and the leaf temperature were monitored on a single leaf in a climate chamber as the temperature was decreased from 20 to 4 °C. The experiment was run simultaneously on the chilling-sensitive Phaseolus vulgaris and on the chilling-tolerant Pisum sativum L. (cv. Shuttle) plants. For both species two phases related to the leaf temperature can be distinguished: the first 4-hour period during which the leaf temperature decreased from 24 to 4 °C, and a second period during which the leaf temperature slightly oscillated around 4°C. The behaviour of F685/F730 for the bean was quite different from that of the pea plant. During the first phase, it decreased markedly for the chilling-sensitive bean while a slight increase was observed for the chilling-resistant pea. In the following period, the F685/F730 values for the pea remained constant while those for the bean were found still to decrease. On the basis of our results, the use of the chlorophyll fluorescence ratio as indicator of plant chilling sensitivity can be envisaged.

Performance evaluation of UV sources for lidar fluorosensing of oil films.

A laboratory experiment is discussed which simulates lidar fluorosensing of oil films on the sea surface at UV wavelengths. Three different mixtures of lasing gases, KrF, XeCl and N2 , were used while a fourth wavelength was given by a dye laser. It turns out that films having a thickness as low as 0.01 microm can be detected; the limiting factor resides mainly in the background fluorescence of water. Best results have been obtained with the XeCl excimer laser.

Hyperspectral fluorescence lidar imaging at the Colosseum, Rome

Fluorescence lidar techniques offer considerable potential for remote, non-invasive diagnostics of stone cultural heritage in the outdoor environment. Here we present the results of a joint Italian-Swedish experiment, deploying two hyperspectral fluorescence lidar imaging systems, for the documentation of past conservation interventions on the Colosseum, Rome. Several portions of the monument were scanned and we show that it was possible to discriminate among masonry materials, reinforcement structures and protective coatings inserted during past conservation interventions, on the basis of their fluorescence signatures, providing useful information for a first quick, large-scale in situ screening of the monument.

Experiments on stony monument monitoring by laser-induced fluorescence

Abstract The use of remote sensing techniques for the monitoring of historical buildings is attractive, since it can allow a fast monitoring of large surfaces without the use of scaffolding and, in addition, a thematic mapping which is easier to read. The studies on fluorescence lidar monitoring of buildings started a few years ago and are still in progress. Interesting results were obtained in biodeteriogen monitoring and in the identification of stones. The possibility of detecting fluorescence thematic images of large areas was demonstrated on both artificial targets and historical buildings. This paper describes the current state of the art on fluorescence lidar monitoring of buildings and the research trends for the near future.

LASER AND INFRARED TECHNIQUES FOR WATER POLLUTION CONTROL

ABSTRACT A remote sensing application for the control of oil pollution and water quality was developed by the National Council of Research at Florence, and the University of Catania, both in Italy....

A fluorescence LIDAR sensor for hyper-spectral time-resolved remote sensing and mapping

In this work we present a LIDAR sensor devised for the acquisition of time resolved laser induced fluorescence spectra. The gating time for the acquisition of the fluorescence spectra can be sequentially delayed in order to achieve fluorescence data that are resolved both in the spectral and temporal domains. The sensor can provide sub-nanometric spectral resolution and nanosecond time resolution. The sensor has also imaging capabilities by means of a computer-controlled motorized steering mirror featuring a biaxial angular scanning with 200 μradiant angular resolution. The measurement can be repeated for each point of a geometric grid in order to collect a hyper-spectral time-resolved map of an extended target.

Fluorescence lidar in vegetation remote sensing: system features and multiplatform operation

Fluorescence lidar is a good tool for the vegetation status control, giving information about stresses even in an early, pre-visual stage. In particular, laboratory and field experiments have pointed out the usefulness of a high spectral resolution system for the analysis of vegetation, allowing more correct and detailed information to be obtained. For this purpose, a high resolution fluorescence lidar has recently been developed at the Research Institute on Electromagnetic Waves, giving good results in field operation on various environmental targets and allowing successful performances from different platforms, including aircraft. Remarkable advances in the monitoring and protection of forests and crops can be achieved by means of a proper airborne lidar system.<<ETX>>