metria: digital photogrammetry for architecture, heritage, engineering and industry

The Walls are a universal symbol and the most outstanding monument of the city of Avila. Its importance probably derives from being the best conserved walled medieval enclosure from Spain and from all Europe.

Raimundo of Burgundy began its construction at the end of the XI century commanded by the king Alfonso VI of Castile, who ordered to repopulate and fortify the cities of Segovia, Avila and Salamanca. Casandro Romano and Florín de Pituenga became site managers according to the traditional historiography. In 1596 Felipe II made restoration works on the wall. It is supposed to be constructed on a military Roman camp layout, with which it coincides in form and proportions, although it is thought that the original Roman wall had less perimeter than the present one. Nowadays the wall has 2,516 m perimeter, 2,500 battlements, 87 towers and 9 doors.

The objectives of our surveying were the true orthophotographic elevations and the cross-sections of the Alcazar and San Vicente doors to a scale of 1:30. The approximate dimensions of the towers are 14x18 meters.

South and north facades of the San Vicente (top) and Alcázar doors (bottom) of the Avila Walls. José Ramón Duralde, Architect.
Clic on the images to enlarge

The doors had North-South orientation and then the facades to survey were East-West oriented. We had to make a suitable planning of the photographs taking regarding to the solar schedule to assure, as far as possible, the minimum radiometric changes on the same facade.

In the inner arcs the photographs taking also became difficult due to the poor lighting conditions and to the small clearance available (3 meters wide approximately in the interior); that is because, in spite of using a wide-angle lens, the number of photographs necessary to compose the final true orthophotograph of those zones was increased.

The monument vertical definition was taken using an horizontal plane laser instead of a plumb line because of the strong wind present on the field work day; even there were falls of small ashlar elements!