What is quite clear is that a major change in the character of the exploration of ancient Jerusalem occurred in the 19th century, with a fascination for the past of the city, fanciful or otherwise, being replaced by that of a scientific concern for the tangible antiquities of the city. The Ordnance Survey conducted by Wilson in 1864 and 1865 marks this turning point. The ancient past of Jerusalem was no longer a matter for armchair scholarly discourse, turning upon the credibility and background of a given scholar, but had now become a matter for clear-cut scientific rigor, which could only be based on facts obtained in empirical fashion, whether through the taking of exact measurements, photography, or excavations in the ground.