Mapping Chimu's settlements for conservation purposes using UAV and close range photogrammetry. The virtual reconstruction of Palacio Tschudi, Chan Chan, Peru

The article deals with the 3D metrical reconstruction of Tschudi Palace, the most famous Palace of Chan Chan archaeological site, in Peru. The complete mapping of the area was performed by integrating aerial data acquired with UAV and terrestrial data captured with close range photogrammetry techniques. The input dataset was acquired during a non-planned survey and with a very cheap equipment. In fact, the acquisitions were made by local and not trained staff. The wind conditions, as well as the presence of visitors made the UAV mission almost impervious so that the huge part of the work consisted on data filtering and cleaning in order to make them suitable to be used for photogrammetric purposes. Afterwards, a tidy process of reconstruction was performed, getting as a final result a thorough ortho-photo of the area. The final check of the model was done with the aid of sketches made some years before by local experts. The accuracy assessment of the overall product is reported as well. Once the model was complete, the ground survey of the Plataforma de Entierro, a buried finding conceived by protective structures, was integrated to the general plan obtained with the first phase. The work demonstrates how it is possible to achieve good results in terms of accuracy and quality even with coarse data. The present study would also serve to be an incentive to those researchers who holds priceless datasets of ancient areas and that should be shared with the research community. As demonstrated, whereas not complete, a 3D survey and the consequent reconstruction can become paramount not to loose the memory of a place that, for different reasons, is under continuous hazards.