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A PORTABLE SOFTWARE SYSTEM FOR A DIGITAL PHOTOGRAMMETRIC STATION 
P. Zatelli, PhD. student, Dept. of Civil and Enviromental Engeneering, University of Trento, via Mesiano 77, 
Trento, Italy. 
Intercommission Working Group II/III 
KEY WORDS: digital, plotter, software, object-space, image matching, portability, multiple images. 
ABSTRACT 
In this paper the design, the realization and the test of a photogrammetric system is presented. This system is built over 
a standard hardware platform using standard programming techniques to obtain a portable system. All the standard 
analytical plotter functions are assured and partially automated, such as image preprocessing, image orientation and 
determination of object space coordinates of single points and of points along linear features. 
1. INTRODUCTION 
This work is part of the digital photogrammetric research 
at the Photogrammetric Laboratory of the Department of 
Civil and Enviromental Engeneering of the University of 
Trento. 
Interest's areas cover: 
e digital sensors calibration and precision analysis of 
the close range photogrammetric techniques; 
e  monoscopic survey of plane objects for strain 
determination of laboratory samples; 
e development of a digital photogrammetric plotter with 
the same functionality of a traditional 
photogrammetric plotter but with the automation of 
some of the tasks and a general ease of use. 
In this paper the development and test of the digital 
photogrammetric plotter is presented. 
2. DESIGN ELEMENTS OF THE SYSTEM 
2.1 Functional design 
The software component of the digital photogrammetric 
system must be suitable for: 
e an efficient user-system interaction via a graphical 
user interface that provides images visualization, 
pointing of the interesting features and general 
controls of the system; 
e image enhancement that makes possible the use of 
all the information in the images, making them more 
readable and increasing the meaning of the details; 
e use of matching algorithms: these techniques 
perform digital image correlation, allowing the 
automation of some tasks and 3D point 
determination by monoscopic pointing; 
e use of image orientation algorithms: this is 
necessary to obtain the functions of a stereoplotter 
(not only those of a comparator): the choosen 
algorithm is a global (relative + absolute) orientation 
performed in a single step by bundles adjustment; 
419 
e data base interface: the system can obtain images 
and other informations directly from existing 
databases, system output must be compatible 
with existing databases; 
The following other tasks are not currently 
implemented but only designed for further 
developments: 
e image trasformation: image normalization helps in 
DEM measurements and all the plotter functions; 
e feature extraction: these operations are usually 
partially automated because of the difficulty in the 
formalization of the a priori knowledge of the 
operator about the objects in the images; 
e results control: gross errors can be automatically 
recognized but the final quality judgment about the 
results must be always given by an operator. 
Some of the digital photogrammetric systems actually 
make use of stereo vision, this solution requires 
dedicated hardware and trained operators. 
In our system the operator observe one image at a time; 
the system itself substitutes the stereo vision by means 
of image correlation; the three main advantages are: 
e no special hardware is required; 
e no special training is required; 
e the simultaneous use of several images is possible. 
In the present version of the system there are no limits in 
the number of images for single points off-line plotting 
and image orientation, while up to three images can be 
used for on-line plotting with oriented images and 
monoscopic observation. 
It must be remarked that the use of three images in the 
plotting operation make the system quite more precise 
and reliable than a system that uses two images only 
thank to the better redundancy. On the other hand a 
system that uses even more images would require a 
more complicated algorithm. 
2.2 Internal design 
The realized system essentially is a software package 
designed keeping in mind the functional requirements 
already explained and the further requirement of 
portability on different hardware platforms and the 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B2. Vienna 1996