1,721,005 research outputs found
Digital Terrain model reconstruction in urban areas from airborne laser scanning data: the method and the example of the town of Pavia (Northern Italy)
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Digital Terrain model reconstruction in urban areas from airborne laser scanning data: the method and an example for Pavia (Northen Italy)
No full textLight detection and ranging (LIDAR) techniques represent a new and fruitful approach in the determination of
digital surface models. One of the goals in processing this data is to set up filtering methods which automatically allows
to extract the ground and the features (buildings, vegetation, etc.) superimposed on the terrain itself. In our work the
emphasis is focused on the first topic. The implemented method takes advantage of the use of spline functions
regularised by means of Tychonov functional in a least-squares approach. Firstly, the DSM pixels have been classified
in order to previously detect any edges of the non-terrain feature. Then all the pixels corresponding to the ground, by
means of a region growing algorithm, has been identified through a correction procedure. Finally, by a new
interpolation on the classified ground pixel only, we can derive the digital terrain model. In the paper the processing
methodology is discussed; and a first extensive example is presented
LIDAR Data Filtering and DTM Interpolation Within GRASS
No full textLIDAR (Light Detection and Ranging) is one of the most recent technologies in
surveying and mapping. LIDAR is based on the combination of three different data
collection tools: a laser scanner mounted on an aircraft, a Global Positioning System
(GPS) used in phase differential kinematic modality to provide the sensor position
and an Inertial Navigation System (INS) to provide the orientation. The laser sends
towards the ground an infrared signal, which is reflected back to the sensor. The time
employed by the signal, given the aircraft position and attitude, allows computation
of the earth point elevation. In standard conditions, taking into account the flight
(speed 200–250 km/hour, altitude 500–2,000 m) and sensor characteristics (scan angle
±
10–20 degrees, emission rate 2,000–50,000 pulses per second), earth elevations
are collected within a density of one point every 0.5–3 m. The technology allows us
therefore to obtain very accurate (5–20 cm) and high resolution Digital Surface
Models (DSM). For many applications, the Digital Terrain Model (DTM) is needed:
we have to automatically detect and discard from the previous DSM all the features
(buildings, trees, etc.) present on the terrain. This paper describes a procedure that
has been implemented within GRASS to construct DTMs from LIDAR source data
Use Of Radar Rainfall Estimate For Hydrological Applications: Preprocessing And Validation
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An hydrological hazard prevention model for the Alpine region: the case of the Lake Maggiore
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