1,721,503 research outputs found
Nécrologie : Louis Lechi
No full textDurry Marcel. Nécrologie : Louis Lechi. In: Mélanges d'archéologie et d'histoire, tome 66, 1954. pp. 323-325
L'économie rurale en Italie. Bibliographie commentée
No full textLechi Francesco. L'économie rurale en Italie. Bibliographie commentée. In: Économie rurale. N°42, 1959. pp. 27-30
Nécrologie : Louis Lechi
No full textDurry Marcel. Nécrologie : Louis Lechi. In: Mélanges d'archéologie et d'histoire, tome 66, 1954. pp. 323-325
Ouverture de la discussion sur l'exposé de G. Weinschenck et J. Kemper
No full textLechi Francesco. Ouverture de la discussion sur l'exposé de G. Weinschenck et J. Kemper. In: Économie rurale. N°150-151, 1982. Agriculture et développement régional en Europe, sous la direction de Louis P. Mahé. pp. 80-81
Effets d'un éventuel élargissement de la CEE
No full textLechi Francesco. Effets d'un éventuel élargissement de la CEE. In: Économie rurale. N°123, 1978. L'agriculture dans les rapports euro-méditerraneens. pp. 60-61
The development of superspectral approaches for the improvement of land cover classification
No full textThis article develops a critical review of the hyperspectral splitting of the solar reflected radiation acquired by hyperspectral imaging sensors. The bandwidth used in the range from 2.0 micrometer to 2.5 micrometer by many hyperspectral sensors sometimes is too narrow for land cover classification. In fact, hyperspectral imagers often suffer from low signal-to-noise in the shortwave infrared region of the e.m. spectrum, resulting in noisy image collection. This paper presents a new methodological approach to the splitting of the solar reflected radiation, called “Superspectral approach”. It is based on the principle of increasing the channel bandwidth by increasing the number of wavelengths, to build synthetic spectral bands with higher SNR. The methodology has been applied to the MIVIS (Multispectral Infrared and Visible Imaging Spectrometer) sensor, an airborne hyperspectral scanner used for environmental remote sensing applications in Italy. Interesting results have been achieved in crop classification, processing the Cordenons survey carried out in August 2001 in the north-eastern part of Italy. The Spectral Angle Mapper (SAM) algorithm was used for classification because insensitive to shadows. For accuracy assessment, the overall accuracy (OA) and kappa coefficient (k) were calculated and used in the comparison. Using the Superspectral approach, an increment in the overall accuracy of about 42% and an increment in the kappa coefficient of about 51% were obtained in comparison to the classification accuracy of unprocessed original MIVIS data (OA=41.21, k=0.35). A second case study is presented using the NASA’s experimental hyperspectral imager HYPERION. Data acquired over the lake of Garda (Italy) in October 2002 was processed with the Superspectral approach. Comparing the simulated HYPERION superspectral bands with the original data, SNR improvements are achieved in the SWIR region (from 0.7 to 54.2 for 2.012 micrometer wavelength and from 0.7 to 64.5 for 2.365 micrometer wavelength). The methodology proposed is sensor independent and can be applied to any of the hyperspectral sensors currently available
Normalized Difference Reflectance: An Approach to Quantitative Change Detection
No full textRemote Sensing is usually used in practice as a tool
for describing and comprehending the land cover status and the
physical properties of Earth’s surface, but not only. The
increasing pressure of human activities on environment and the
need to forecast, monitor and manage natural hazards - often due
to climate change - have forced the scientific community to focus
its attention on the study of environmental dynamics and timeseries,
thus giving great importance to Change Detection
Techniques.
This paper introduces a simple and effective approach to Change
Detection from satellite images: the Normalized Difference
Reflectance (NDR), a multi-spectral quantitative way to describe
radiometric variation of surface features, variation that has to be
interpreted then in order to distinguish real changes in land
cover from changes related to other variations.
Pre-processed multi-spectral and multi-date ASTER and ETM+
data were subjected to parametric radiometric normalization
and hence converted to NDR values; these values were used then
as a base for applying supervised or unsupervised classification
methods to produce change maps of the areas investigated. A
case study regarding a flood event and one other dealing with
urban expansion were analyzed and assessed
A DNA algorithm for the batimetric mapping in the lagoon of Venice using QuickBird multispectral data.
Full text linkDuring the last decade, several studies have focused on the use of passive multispectral remote sensing to derive the bathymetry in coastal zone. In particular, data acquired with the SPOT and the Landsat TM/ETM+ sensors have been used to derive models of bathymetry at medium scales. Until now, the successful application of passive remote sensing techniques to bathymetry mapping was restricted to costal zones with clear water and small changes in the seabed, but with the availability of the high resolution satellites (IKONOS, Eros-A1, QuickBird, SPOT-5), researchers have a new powerful tools to study environmental phenomenon at large scale. This paper focus on the use of high resolution imagery to estimate water depths in a lagoon environment. Starting from the depth of penetration zone method proposed by Jupp for costal bathymetry mapping, a new genetic algorithm was developed for lagoon bathymetry mapping. The potential use of the QuickBird multispectral data, together with the new algorithm developed, was tested in a complex environment such as the lagoon of Venice (Italy). Several tests have been performed into five different test sites (S.Erasmo littoral, Treporti canal, S. Felice canal, Canesa canal and Bari canal), where 18 radiometric transects were traced to study the lagoon bathymetry. The accuracy of the batimetric measures was assessed by using other known soundings depth points within the test area. An interesting correlation between the real and the computed bathymetry was found. The limit of a such analysis lies in the correct calibration of the model, that, for the complex lagoon ecosystem, is not a simple task
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