Abstract
This article focuses on the use of Terrestrial Laser Scanning (TLS) for change detection analysis of multitemporal point clouds datasets. Two topographic surveys were carried out during the years 2016 and 2017 in an underground marble quarry of the Apuan Alps (Italy) combining TLS with Global Navigation Satellite System (GNSS) and Total Station (TS) studies. Multitemporal 3D point clouds were processed and compared with the aim of identifying areas subjected to significant material extraction. Point clouds representing changed areas were converted into triangular meshes in order to compute the volume of extracted material over one year of quarrying activities. General purpose of this work is to show a valid method to examine the morphological changes due to raw material extraction with the focus of highlighting benefits, accuracies and drawbacks. The purpose of the executed survey was that of supporting the planning of quarrying activities in respect of regional rules, safety and commercial reasons.
Highlights
The use of Terrestrial Laser Scanning (TLS) data for the determination of morphological variations is gaining increasing interest in geological surveying and monitoring
Taking into account that the width of the quarry tunnels is on average 10 m, TLS was generally placed at the center of the quarry tunnels in such a way that targets were acquired at a distance of about 5 m, resulting in a point spacing of about 1.8 mm
TLS point clouds have an accuracy of a few millimeters with a mutual misalignment of 3.5 cm
Summary
The use of Terrestrial Laser Scanning (TLS) data for the determination of morphological variations is gaining increasing interest in geological surveying and monitoring. The scanner measures the time a laser pulse takes to travel from a source to a reflective surface and back again (round trip); from the knowledge of the time, given that the velocity is equal to the speed of light, the distance between the source and the target can be computed. The working principle of the second type is based on the modulation in amplitude of the emitted (incoherent) light; the scattered reflection from a surface is collected and the system measures the phase difference between the sent and received waveforms, the delay time. The TLS survey was carried out using a pulse-based static device which measures the range between source and target through an infrared light. With the goal of generating realistic virtual reality
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