Control of Laser Scanner Trilateration Networks for Accurate Georeferencing of Caves: Application to El Castillo Cave (Spain)

Abstract

There is a growing demand for measurements of natural and built elements, which require quantifiable accuracy and reliability, within various fields of application. Measurements from 3D Terrestrial Laser Scanner come in a point cloud, and different types of surfaces such as spheres or planes can be modelled. Due to the occlusions and/or limited field of view, it is seldom possible to survey a complete feature from one location, and information has to be acquired from multiple points of view and later co-registered and geo-referenced to obtain a consistent coordinate system. The aim of this paper is not to match point clouds, but to show a methodology to adjust, following the traditional topo-geodetic methods, 3DTLS data by modelling references such as calibrated spheres and checker-boards to generate a 3D trilateration network from them to derive accuracy and reliability measurements and post-adjustment statistical analysis. The method tries to find the function that best fits the measured data, taking into account not only that the measurements made in the field are not perfect, but that each one of them has a different deviation depending on the adjustment of each reference, so they have to be weighted accordingly.

A Multisensory Analysis of the Moisture Course of the Cave of Altamira (Spain): Implications for Its Conservation

“…The significance of maintaining a highly precise cartographic model of the cave manifests when projecting knowledge-based models that rely on georeferenced parameters, encompassing aspects such as microbiological, climatic, hydrochemical, geomorphological, and geophysical data [58].…”

“…The reflection amplitudes and intensities of GPR signals are proportional to the contrasts in dielectric permittivities at reflector boundaries and are dependent on the reflection coefficients. Since most GPR studies are carried out in nonmagnetic media (low-loss media), the approximate expressions for the electromagnetic impedance (Z) and reflection coefficient (R) for two media are given by [58,59]:…”

Tracking the Evolution of Biodeterioration and Physico-Chemical Alterations Using Microphotogrammetric Techniques in the Altamira Cave

“…The geomatics technologies used to create the reference frame [3][4][5] and the derived studies [6,7], are not the subject of this article. However, a summary is given below:…”

Integration of Remote-Sensing Techniques for the Preventive Conservation of Paleolithic Cave Art in the Karst of the Altamira Cave

“…The field campaign was carried out in December 2013; a FARO FOCUS X-130 [36] was used, and 300 scans were required. Calibrated spheres were used as tie points and the traverse checkerboards as references, which were adjusted with an accuracy of 2.7 mm for 95% of the points (Figure 2a) [37].…”