Subsea spectral identification of shipwreck objects using laser-induced breakdown spectroscopy and linear discriminant analysis

M. López-Claros, F. J. Fortes, J.J. Laserna, Journal of Cultural Heritage, 2018, 29, 75 – 81


Underwater LIBS is an evolving technology which offers unique advantages over traditional methods, notonly do it offers the composition of liquids with high reliability; it also provides the elemental compositionof solids with little or no user manipulation. Because of this advantage, LIBS has been used as a tool forinspecting materials in underwater archaeology, where knowledge of the chemical composition mayprovide valuable clues on the origin of materials in shipwrecks and submerged buildings. This studyattempts to provide undersea LIBS instrumentation with the data processing tools intended to makeshipwreck inspection surveys easier and faster. The new tool has been designed to sort the readingsobtained by a LIBS system when inspecting unknown pieces found in the sea bottom and assign theircomposition to one of several groups of common materials found in shipwrecks. The tool involves lineardiscriminant analysis that was first validated in the laboratory with a training set of samples collectedfrom wreckages. Then, the method was used in an underwater survey in the Mediterranean Sea to sort thematerials found in a shipwreck. In combination with high-definition video recording, this approach canprovide an understanding of the materials and a permanent record of the unknown assets, this eliminatingthe need for underwater archaeologists to make handwritten notes of individual pieces while surveyingshipwrecks.

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