269 
VALUATION OF ORTHORECTIFICATION 
BY USE OF PHOTOMODELER SOFTWARE 
Herbert J. B. Erwes, Walter da Silva Prado, 
Arly Gáutama Rodrigues e Silva, Daniel Wander Ferreira de Meló, 
Instituto Militar de Engenharia (IME), Departamento de Engenharia Cartográfica 
Praça General Tibúrcio, 80 - Praia Vermelha, 22290-270 Rio de Janeiro / Brazil, 
Tel/Fax 0055 21 2546 7069 
e-mail: d6walter@epq.ime.eb.br 
KEY WORDS: Close - Range Photogrammetry, Architectural Photogrammetry, Surveying Methods, 
PhotoModeler, 3x3 Rules, Didactic Project. 
ABSTRACT: 
Within the project “Initiation to Research” students and their tutors had to produce an orthophoto at scale 1:200 of the 
main façade of the institute as a training project. The dimensions of the object are 107m long and 23m high. 
The available equipment of the institute was: 
Digital Camera KODAK DC 265 
- Digital Camera SONY DSC P-71 
- Total Station LEICA Model TCR 307 
Software PhotoModeler, version 4.0 d 
Software DVP with Orthophoto Module. 
In the planning stage of the project, it was decided that the façade had to be divided into three parts, due to the rather 
large dimension of the object, short camera-to-object distances, obstructions (trees, parked cars, etc). 
The chapter Ground Control is treated with high emphasis and may be of special interest. 
The spatial coordinates of 30 well distributed targets and 12 more points in the object were determined by forward 
intersection and polar measurement by use of an electronic distancer (EDM) in reflector-less mode and simultaneous 
trigonometric levelling. 
The results are compared and discussed. Two coordinate systems with different characteristics, but with the same 
vertical datum were used: 
- An arbitrary local survey system served as the purpose for calculation of the results of measurements in the field. 
- The object system, defined in the object, represents the final values of coordinates for processing within the program 
PhotoModeler. 
Various methods of transformation between the two systems, such as: 
- plane similarity coordinate transformation with 2 identical points 
- plane similarity transformation with over-determination (HELMERT-Transformation). 
- plane affine transformation with over-determination (HELMERT-Transformation). 
were employed and compared. Having the same origin in altitude, the two sets of coordinates could be treated as plane 
coordinates. 
Furthermore, some values of transformed coordinates could be checked in the field by use of the program 
“Determination of Free Station Coordinates” of Total Station LEICA TCR 307. 
The achieved precisions of the ground control coordinates are adequate to the scale 1:200 of orthophoto. 
Summarizing the chapter Ground Control, it can be stated that a simplified ground control could be useful for small 
objects within the 3 x 3 Rules. Also the way to get an efficient ground control for large objects is shown. 
A large number of orthogonal and oblique images were taken. 
An orthophotomosaic, composed of various orthophotos produced by PhotoModeler, served for the plot of the façade. 
1. INTRODUCTION 
Within the project “Initiation to Research" students and 
their tutors had to produce an orthophoto at scale 1:2oo of 
the main façade of the institute as a training project. The 
dimensions of the object are 107 m long and 23 m high. 
The available equipment for this project was: 
Digital Cameras : KODAK DC 265 
SONY DSC P-71 
Total Station : LEICA model TCR 307 
Softwares : PhotoModeler, version 4.0 d, 
DVP with Orthophoto Module