Graphic survey and three-dimensional modelling of the Negro Tower or Arraez, post-coastal tower of the sixteenth century in El Algar (Region of Murcia, Spain)

Abstract

Post-coastal towers or rural fortress towers, built in the sixteenth century on the Mediterranean coast, had the mission of protecting the population and enhancing the repopulation of these areas, heavily punished by incursions by berber pirates. The Negro Tower or Arraez Tower, in El Algar-Cartagena (Region of Murcia, Spain), is one of those post-coastal lookout towers and was built in 1585. It is shaped like a truncated pyramid, square plan and a height of about 14,00 m. Originally, it had three floors and a terrace. Despite its degree of protection (it is a monument), its current state of conservation is semi-ruined. It has no cover, the vault of the first floor has collapsed and presents cracks that threaten its stability. Therefore, a research project has been developed that has included, among other aspects, the graphic survey with two complementary techniques: digital photogrammetry and 3D laser scanning. The result is an exhaustive graphic documentation that allows understanding the construction and allows the consolidation and volumetric recomposition of the tower. With this work, it is intended to contribute to the conservation and recovery of the heritage value of the Tower, as well as the integration of the historical monument in its natural and landscape environment.