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Nicola Coscini, Autorità di Bacino Pilota del Fiume Serchio (Italy)
Stefano Sadun, Autorità di Bacino Pilota del Fiume Serchio (Italy)
Nicola Del Seppia, Autorità di Bacino Pilota del Fiume Serchio (Italy)
Francesco Falaschi, Autorità di Bacino Pilota del Fiume Serchio (Italy)
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Along the 2006, the Serchio River Basin Authority (Italian Department of the Environment) has undertaken a LIDAR (Light Detection and Ranging) aerial survey into a wide area (about 28.000 hectares) of its basin of jurisdiction. The survey, commissioned to the Compagnia Generale Riprese Aeree (Parma, Italy), principally consist of wide areas of the ploodplain of the Serchio River and its majors tributaries.
The LIDAR survey is believed one of the most important technique concerning the high precision digital surface modelling, the monitoring of the natural riverbed evolution or transformation of the floodplain due to the human activities, hydraulic modelling of flood propagation, and mapping of inundated areas.
The main producs derived from LIDAR survey have been: high precision Digital Surface Model (DSM) completed with buildings and vegetation, a filtered DSM obtained by removing vegetation, and a Digital Terrain Model (DTM) derived from the DSM by post-processing. Accuracy is about ∼ 20cm for the heights and cells area is 1m2. DSM and DTM products are provided whether in WGS84 system (ellipsoidical heights, WGS84-Ellipsoid), or in Gauss-Boaga system (geoidical heights).
Particular attention was reserved to the problem of the coordinates accouracy. Actually, at the same time the aerial LIDAR survey was performed, data about ground-GPS station (geodetic control station) were recorded. Moreover, in order to obtain the best fitting between the derived surface models and x, y, z data-sources, a local transformation of the geoidical model was performed. Finally, the LIDAR products quality in terms of data precision was verified using ground-based topographical information.
Extra steps in verification procedure are listed as follows: topographical survey on sample areas; ground- based DTM computing with the same cell size as LIDAR surface model to verify; matching of DTM and DSM derived from LIDAR and the ground-based DTM; matching of features coordinates on LIDAR products with well-known ground-based coordinates belonging to the topographical survey.
Most of the sample areas resulted in excellent data accouracy and precision. Results always stay constant even if the numerical interpolator chosen for the digital surface modelling vary. Moreover, LIDAR products highlight the capability of reconstructing high precision hydraulic section of the river with the advantage of a more quickly analysis of the information related.
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