Promoting the heritage of the city of San Cristobal de La Laguna through a temporal link with a 16th century map.

Abstract

There is an increasing interest in the conservation of historical cities since they provide a link to the roots of their communities and bring their inhabitants cultural and economic growth. In this paper, the authors present an approach to promote the knowledge of the UNESCO World Heritage city of San Cristóbal de La Laguna in the Canary Islands, Spain. The city was founded in 1496 and has a unique value due to its urban design. This work introduces a web application that allows a user to locate places and addresses of the current city in its first known map authored by Leonardo Torriani in the 16th century. To build this application we have georeferenced the ancient map in the current cartography. The georeferencing process needs the identification of homologous ground control points in the coordinate systems of both the old map and the current cartography, as well as the definition of a transformation between them. Best results were obtained with the non-parametric natural transformation interpolation, leading to a global mean error of 4.9 m reduced to 3.2 m in the historical city centre. To provide a fast response to the user of the web application, a technique to precompute offline the natural transformation is presented. The web application has a simple front-end where the user enters the current city address in a form. This activates a query to obtain the geographical coordinates of the address that are transformed into map coordinates using the pre-computed transformation. These map coordinates are used by a map viewer in the front end that locates the user address in the ancient map. To test the performance of the web application, the load of the system has been analysed obtaining a latency of 1.4 s in 50 concurrent users. Results show that the web application provides accurate results in the historical centre while offering satisfactory response times.