LiDAR, acronym for Light Detection and Ranging or Laser Imaging Detection and Ranging, is an "active" remote sensing technique for carrying out high resolution topographic surveys. In this abstract we will briefly illustrated this technology and its fields of use.

LiDAR technology is a laser scanning technique that allows you to analyze an area by obtaining a point cloud.

Each point will bring with the coordinates and height. The data acquisition system is composed of a laser scanner that emits a high frequency pulse, a GPS for positioning the point and ground GPS stations positioned on the vertices of the geodedic network.

The laser scanner is positioned on board an airplane or drone and is composed of a transmitter (the laser), a receiver consisting of a telescope and a data acquisition system.

The pulses sent by the laser are high frequency, between 10 and 150 kHz; for studies on surface morphology there are wavelengths between 1.0 and 1.5 µm while for bathymorphological studies they range from 0.50 and 0.55 µm.[1]

Next of coastal areas, especially in the case of a coast composed of cliffs, the reliefs are affected by errors caused by the refraction of the sharp surfaces and by the water. In these cases, aerial surveys are integrated with sea surveys by positioning the laser scanner on a boat.

The utility of this type of technology is due to the fact that it is possible reproduce the environment in an extremely detailed way. In fact it is possible to obtain and divide, for example, vegetation from buildings and divide buildings and vegetation from the earth's surface. This happens because each pulse returns an echo of the surface on which it is bounced, for example if the vegetation is not excessively dense, it is possible to obtain branches, leaves and the ground on which the tree rests.

In the post-processing phase, all the information captured can be separated in order to obtain a DSM (Digital Surface Model) and a DTM (Digital Terrain Model). The following images show two hillshades obtained by processing the LiDAR point cloud of two different echoes:

How can you note in figure 2 buildings and vegetation are clearly visible, completely absent in figure 3.

Have the possibility to reproduce in such a way faithful an area opens up the use of LiDAR to many fields:

• Updating DEMs (Digital Elevation Model);
• Glacier monitoring;
• Forestry census;
• Analysis and monitoring of landslides;
• Urban development.

These and other aspects can be represented and studied with LiDAR.

The availability of such data on the National Geoportal is quite limited, from the union paintings you can note that not all national soil has been examined and not all of the areas examined are at 1x1 resolution. Given their great usefulness, these data should be completed and made available for all relevant studies.

Other very important data, but absent within the Geoportal, are the bathymorphological data detected with the Multibeam technique. Multibeam is a technique similar to LiDAR technology that allows you to detect the morphology of the seabed with the use of sonar. Also in this case, depending on the echo, you can obtain more layers of information relating to the seabed being examined.

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[1] “LIDAR: an introduction and overview” presented by Keith Marcoe GEOG581, Fall 2007. Portland State University