Comparative Study of Graphic Representation Methods on Architectural Heritage

Introduction

The graphical representation of architecture has been a necessity for centuries, either as a sign of artistic expression or as a method of documentation and study. Sketches, drawings, maps, plans, engravings and paintings were the methods of graphic representation used for centuries (Garfella, Máñez, Cabeza, & Soler, 2012) The advent of photography was a technical breakthrough as a method for documenting artistic and, more particularly, architectural heritage since it made it possible to capture images that were very similar to how scenes are perceived by the human eye, as well as allowing three-dimensional images and the photogrammetric rectification of buildings, which in turn enables us to take measurements directly from them (Lerma, 2002).These systems of representation have progressed exponentially with the development of both cutting edge optical and photographic optical equipment and the development of powerful computers and highly specific and advanced graphics software.

The purpose of this paper is to analyse the use of different graphic survey methods, both traditional and advanced, in the graphic surveying of architectural heritage applied to a case study, namely, the side Portal of the Church of Our Lady of the Assumption in Vistavella del Maestrazgo in the province of Castellón (Spain).The volume and dimensions of this retablo-portal dating from the years 1604-1624 and of Renaissance style have made it an excellent testing ground for our study.

As initial data we used a number of old photographs that were found in historical archives as well as in different publications.

For the study, we carried out surveys using traditional methods, such as freehand sketches that were dimensioned manually with measuring tapes, distance meters, levels, plumb-lines and archaeologists’ combs, and the later scaling of the façade from the field data. Anaglyph images were also created using both old scanned photographs and modern digital images.

Photogrammetric surveys were also carried out, which allowed us to rectify the item using specific software. Photogrammetric restitution of the façade was also performed using the Photomodeler program, which enabled us both to create three-dimensional images of this architectural element and to generate a cloud by spatial mesh points that define this element with precision.

Another technique used was to survey the façade by means of a 3D scanner. This was performed with the aid of topographic support equipment, such as a Trimble DR Model 5603 STD Robotic Autolock with a precision of 3” (1.0 mgon) direct laser reflectorless total station; a laser imaging total station with two internal panoramic digital cameras and an apparent resolution equivalent to 4.8 Mp, with Topcon IS-203 reflectorless measurement with an angular accuracy of ± 3”, and finally a class one long-range pulsed invisible laser Topcon GLS 1500-type 3D terrestrial scanner, with an accuracy of 4 mm at a scanning range of up to 150 m angular and an angular precision of 6” (2.0 mgon), associated with a coaxially aligned built-in 2.0-megapixel digital camera. Data collection was also completed with a 10.2-megapixel Nikon D-80 digital photographic camera and a 24-megapixel Nikon D-5200 with a conventional lens with a focal length of 18-135 mm and an aperture of f/3.5-5.6, and a wide-angle Sigma with an 8-16 mm lens and focal aperture of f/4.5 to 5.6. This equipment allowed us to generate three-dimensional images and three-dimensional meshes of points.

Finally, we employed SfM (Structure for Motion) systems or low-cost graphic surveying systems through the use of digital photographs and different commercial software applications that enable the user a simple way to generate, like the previous systems, and edit both three-dimensional images and meshes or point clouds.

Based on the three-dimensional data thus obtained, we were able to make plans showing elevations, layouts and sections, as well as scale models using different 3D printing systems.