This paper presents a distance-constrained bundle adjustment approach which was used to calibrate a multi-sensor system. The multi-sensor system integrates three rigidly fixed cameras, two visible and one thermal infrared. The influence of the number of camera base constraints is empirically analysed through the process of self-calibration bundle adjustment. The successful calibration of the multi-sensor system requires the incorporation of a full set of baseline distance constraints into the adjustment to obtain satisfactory computations of the camera bases and relative rotations between cameras. The improvement in the precision of the calibration is outstanding; its maximum is achieved with the low-resolution thermal camera. This constrained solution is recommended for multi-sensor systems that integrate rigidly fixed cameras.
Highlights Convergent SfM provides reliable DEMs for microscale geomorphic change detection. Reliable results require rigorous DEMs georeferencing in a local reference system. Comparison with dragged sediment in runoff shows good agreement. Basic LOD min thresholding shows right performance to detect tiny changes.
ABSTRACT:A case study to evaluate the use of microfading spectrometry (MFS) for the study of colored systems found in prehistoric rock art paintings was conducted in the Cova Remígia rock-shelter, Castellón (Spain). This rock shelter is part of the rock art sites of the Mediterranean basin on the Iberian Peninsula included in UNESCO's World Heritage List. Some of the paintings belonging to this group are exposed to environmental factors including natural daylight, wind and rain, depending on the time of the day and the season of the year. Therefore, their preservation is a major concern to stakeholders and researchers responsible for protecting and studying these prehistoric paintings. The experimental work in Cova Remigia focused on measuring the reflectance curves (400-700 nm) and determining the photostability of various areas containing red and black pigments on the rock art paintings. The preliminary results indicate that MFS is a suitable technique for studying the response to light of rock/pigment systems found in rock art sites. The advantages and limitations of the technique are discussed.
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