OIA AND BUILDING: TWO PROGRAMS FOR HOUGH APPLICATION TEACHING IN 
DIGITAL PHOTOGRAMMETRY 
Pérez-García, J.L.; Delgado-García, J. & Cardenal, J. 
Dpto. Ingeniería Cartográfica, Geodésica y Fotogrametría. Escuela Politécnica Superior. Universidad de Jaén. c/ Virgen de la 
Cabeza, 2 - 23071 Jaén (Spain). e-mail: jIperez(@ujaen.es; jdelgado@ujaen.es; jeardena@ujaen.es 
Commission VI, WG VI/4 
KEY WORDS: Photogrammetry, Education, Software, Transformation, Algorithms, Automation 
ABSTRACT: 
In the last decades, the photogrammetry has experienced important changes. The analytical photogrammetry, and afterwards the 
digital photogrammetry, has revolutionized the methods, processes and products of the photogrammetric works. These changes must 
be reflected in the educative university programs dedicated to the study of photogrammetry. In such a way that future technicians 
can receive an advisable and modern education. The main problems appear because most of the processes in digital photogrammetry 
are complex, and are solved generally by the digital photogrammetric systems (DPS) of internal way (black-box). In this context, the 
users (and the students, too) have a limited access to the applied procedures and the obtained partial results, making difficult the 
correct understanding and learning. A fundamental work of the professors dedicated to the education of the digital photogrammetry 
is to provide the adequate tools that allow to learn the basic processes through open software in which the student can have a total 
access to the individual operations (in most of the cases related directly to the treatment of the digital image) as well as to the partial 
results. With this aim, this paper is about two software applications: OIA program dedicated to the automatic interior orientation of 
images of metric and non metric cameras, and BUILDING program, dedicated to the automatic extraction of buildings, using the 
extraction of edges and prismatic models. The final objective of both programs is the knowledge of the Hough transformation 
application to the Digital Photogrammetry. OIA constitutes complete interior orientation software that uses the Hough Transform for 
the recognition and measurement of the basic elements that compose the fiduciales marks (circles and lines). This application also 
allows working with non metric images. In this case, the interior orientation is made by means of the location and measurement of 
the edges of the image. The program allows the interaction of the operator to know the partial results as well as the final 
transformation. BUILDING present a more complex application of the Hough transform, the automatic extraction of buildings by 
means of the extraction of edges in an oriented image using a digital model surface of the zone as additional information. 
I. INTRODUCTION paper are: a) the inner orientation of metric and non-metric 
images; b) the location and prismatic modelling of buildings in 
The photogrammetric processes automation has experienced in. Urban zones (with isolated buildings). 
the last years a large development thanks to the digital 
photogrammetry and to the advance of the technology in 2. METODOLOGY 
general and computing in particular. 
One of the most used methodologies, for edge extraction (lines 
and circles) in digital imagery is the Hough transform (Hough, 
1962). Elements extraction begins as an image processing 
operation. It can be carried out in various ways depending on 
assumptions about the imaging process and how the elements 
will be used in the algorithm. Using an edge operator, a point 
dataset can be extracted from the digital image. This dataset 
includes points that have certain differences with the 
surroundings pixels and, for this reason, they can be considered 
as “potential edges”. The basic objective of the Hough 
transform is to establish which points of the previously 
extracted dataset belong to the same geometric element (line, 
curve,...). This geometric element will be expressed as a 
parametric function. All the points of the dataset are transferred 
from the image space into a parametric space. The parameters 
that we need to describe the geometric element are added to an 
accumulated table using a predetermined discretization. The 
cells of this table that contain the maximum values indicate the 
most frequent parameters and define possible geometric 
This automation has produced that the basic photogrammetric 
processes (such as, interior, relative and absolute orientation, 
digital elevation models and orthoimages generation, etc.) have 
been converted into a black-box processes. In these processes, 
the operator has not access to the partial results, nor to the 
methodology used by the digital photogrammetric system. This 
lack of knowledge of the used methodology, can difficult the 
correct analysis of the obtained results for the operator in order 
to detect the presence of errors. Photogrammetry teaching must 
provide tools that allow solving this problem. It is basic the 
entire knowledge of the process and the results, both partial 
results and final products. Using these tools, the educators can 
show, in a detailed form, the different steps involved in the 
complex digital photogrammetric processes and the students 
can obtain an adequate understanding of the problem and 
processes. In this paper, we present two applications specially 
designed in order to allow to the students a total access to the 
entire process and partial results. The objectives of the 
automatic processes of the applications that we present in this 
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