inbul 2004 
DIGITAL DEVELOPMENT OF A SMALL VALENCIAN TOWER 
J.T. Lerma, R. V. Tortosa 
ETSI Geodésica, Cartográfica y Topográfica. Universidad Politécnica de Valencia. 
C? de Vera, s/n. 46022, Valencia (Spain) 
jllerma@cgf.upv.es 
KEY WORDS: Close Range Photogrammetry, Architecture, Archaeology, Cultural Heritage, Visualization, Documentation 
ABSTRACT: 
Warping of images dealing with cylindrical objects through monoplotting is an efficient tool for archiving, documenting and 
analysing non-planar but mathematical surfaces. However, it is not usually implemented in most of the photogrammetric packages, 
although there are many architectural objects, monuments and buildings, as well as industrial features inadequate for orthoprojection 
but appropriate for development or cartographic projection. 
This paper shows the background and the results of a new photogrammetric software called DesenRec (‘Desenvolupament i 
Rectificació', Development and Rectification), ideal for full development of cylindrical shapes. A set of eight images was taken in 
order to test, record and mosaic the outer walls of a small tower placed in the Valencia City centre. The tower is 6 m high with a 
diameter of approximately 2 m. After warping each image a digital mosaic was created to plot and analyse the whole tower's shape. 
1. INTRODUCTION 
Terrestrial and close range photogrammetry are both much 
more efficient and economic than a few decades ago, mainly 
due to the advance of digital technology and the development 
of powerful processing packages. Nowadays, the use of non- 
metric cameras, without lack of rigorousness, opens new 
market photogrammetric demands. Moreover, there are more 
technicians interested in applying photogrammetric 
procedures to their field of work. This reality can be verified 
in specific markets such as architectural photogrammetry, 
archaeological photogrammetry and/or industrial 
photogrammetry, for instance. 
The employment of digital images allows the generation of 
high quality raster products, adding colour and texture 
variables to the traditional line plottings. In the case of 
architectural and archaeological documentation, digital 
images themselves are an essential document in order to ease 
the study of materials and damages, interpretations and 
analysis of Cultural Heritage. 
Projective transformation or rectification of images 
corresponding to planar objects is a simple technique that 
makes easy the documentation of walls, panels and facades. 
In literature can be found many related examples, and its 
mathematical model is well known (Lerma, 2002). 
Unfortunately, not all the objects are planar or can be 
partially considered planar. The existence of relief requires 
other strategies to derive the digital model before warping, 
e.g. stereoscopy, multi-monoscopic measurements. However, 
it is also possible to take another approach: the unwrapping 
or monoplotting of developable surfaces (Karras er al, 1997; 
Hemmleb and Wiedemann, 1997). This is particularly 
Interesting for documenting curved surfaces and frescoes, 
arches, towers, chimneys, etc. Whenever parametric surfaces 
such as cylindrical, spherical or conical ones can be found, 
the development of original images is feasible. 
This paper tackles the plotting of mathematical surfaces 
particularised to the case of cylindrical objects. In fact, a set 
of eight images was taken in order to test, record and mosaic 
the outer walls of a small Valencian tower. 
2. SOFTWARE DESIGN 
We have ourselves designed and developed a new 
photogrammetric application called DesenRec 
(Desenvolupament i  Rectificatió, Development and 
Rectification) in order to solve, on the one hand, two- 
dimensional transformations of planar objects, and, on the 
other hand, digital developments of cylindrical objects. The 
program is based upon monoscopic procedures and digital 
images. The software DesenRec 1.0 (Figure 1) offers the 
following features: 
- A Object oriented language program. 
- Camera calibration algorithms. 
- Best mathematical fitting to features or 
objects (planar and non-planar but 
continuous). 
- Determination of transformation 
parameters between image and object. 
- Gross error detection and statistical 
analysis. 
- Digital image development and/or 
resampling. 
- Image mosaicking. 
Besides, it is not necessary to be an expert in close range 
photogrammetry in order to run successfully the program. 
Furthermore, it accepts many ways of control information 
based on both image and object space. 
3. TEST APPLICATION 
Software DesenRec has been tested on many emblematic 
monuments located at the Valencia region. The main 
characteristic of all of them is that they can be modelled by 
means of a unique mathematical expression.