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3.2 Creation of vector model
The vector model was created by processing of scanned
photographs, which were taken by photogrammetric cameras.
For these purposes were used UMK 10/1318 of Zeiss-Jena and
stereometric camera SMK 5,5/0808 with 40 cm baselength,
which is Zeiss-Jena production. The usage of colour pictures
was not very convenient because of small distances for taking
the photograps that did not allow capturing whole wall in one
photo. By these reason the traditional photogrammetric cameras
were used. For mapping of photos was used software product
DVP (Digital Video Plotter) of DVP Geomatics Inc. (Leica,
1995). The used version of this product is (working in DOS
mode) is developed for processing of separate stereo images. It
is convenient for mapping of separate facades of the object. The
vector models of facades are produced. The control points,
measured with surveying methods, were used to connect models
of separate facades. All models of facades were transformed to
local coordinate system of grid model.
3.3 Binding Photo-textures with Grid model
Binding of photo-textures with vector model requires assigning
of textures to model surfaces and geometrical connection
between the photo-textures and corresponding surfaces.
Different software products could be used for these purposes.
The requirements that these products must satisfy include are
possibilities for such binding, easy creation of final model and
possibilities for export in format compatible Internet browsers.
Possible candidates are AutoCAD Land Development with
AutoCAD Overlay, 3D Studio MAX and Micro Station.
Highest flexibility shows 3D Studio MAX but this product
requires very long period of training and is not very convenient
for education in Geodesy. By these reasons in educational
process are included initially Micro Station of Bentley and
AutoCAD Overlay. The choice of the product depends on the
environment in which the vector model is produced and
processed. DVP product does not export directly *.dgn format
but creates *.dxf file. Micro Station allows importing of *.dxf
format and all following processing is made in the environment
of Micro Station.
To create adequate model it is necessary to crop the photo-
texture by the boundaries of surface. For educational purposes
is used Photoshop. The boundaries are overlapped over the
raster layer by converting the vector model to raster layer. The
results for the west wall of the church “The Assumption of the
Virgin Mary" are shown on the Figure |.
Figure 1. Transformed image of west wall
4. TRAINING FOR DIGITAL ORTHOPHOTO
PRODUCTION
Digital orthorectification produces the most precise results for
orthophoto maps. The main importance for the accuracy of this
process is the quality of digital terrain model. The Ortho Engine
of PCI Geomatics was used for education purposes in
preparation of orthophoto for cadastral purposes
(Marinov, B.D., Draganova, N.P., 2003).
49
Cut image of west wall
4.1 Processing Steps for Aerial Triangulation
The inner orientation with Ortho Engine allows examination the
influence of different number of points over the residuals (PCI
— Geomatics, 2001). The accurate measurements of fiducial
marks decrease the errors of transformation. Disadvantage of
inner orientation stage is that it is not possible to select type of
transformation and operator could not estimate the difference in
errors for different transformations.