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Alveolite T-linfocitaria nel lavaggio broncoalveolare di pazienti affetti da farmer's lung
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Automated DEM extraction in digital aerial photogrammetry: precisions and validation for mass movement monitoring
No full textAutomated procedures for photogrammetric image processing and Digital Elevation Models (DEM) extraction
yield high precision terrain models in a short time, reducing manual editing; their accuracy is strictly related to
image quality and terrain features. After an analysis of the performance of the Digital Photogrammetric Workstation
(DPW) 770 Helava, the paper compares DEMs derived from different surveys and registered in the same
reference system. In the case of stable area, the distribution of height residuals, their mean and standard deviation
values, indicate that the theoretical accuracy is achievable automatically when terrain is characterized by
regular morphology. Steep slopes, corrugated surfaces, vegetation and shadows can degrade results, even if manual
editing procedures are applied. The comparison of multi-temporal DEMs on unstable areas allows the monitoring
of surface deformation and morphological change
Effects of surface irregularities on intensity data from laser scanning: an experimental approach.
Full text linkThe results of an experiment carried out with the aim to investigate the role of surface irregularities on the intensity data provided by a terrestrial laser scanner (TLS) survey are reported here. Depending on surface roughness, the interaction between an electromagnetic wave and microscopic irregularities leads to a Lambertian-like diffusive light reflection, allowing the TLS to receive the backscattered component of the signal. The described experiment consists in a series of TLS-based acquisitions of a rotating artificial target specifically conceived in order to highlight the effects on the intensity data due to surface irregularity. This target is articulated in a flat plate and in an irregular surface, whose macro-roughness has a characteristic length with the same order of the spot size. Results point out the different behavior of the plates. The intensity of the signal backscattered by the planar element decreases if the incidence angle increases, whereas the intensity of the signal backscattered by the irregular surface is almost constant if the incidence angle varies. Since the typical surfaces acquired in a geological/geophysical survey are generally irregular, these results imply that the intensity data can be easily used in order to evaluate the reflectance of the material at the considered wavelength, e.g. for pattern recognition purposes
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