4. THE GRAPHICAL USER INTERFACE - GUI
A friendly GUI-Dialog Box with a number of push-buttons
provides a user-friendly window-manager interface and
powerful event-driven functions for facade's modeling
manipulation.
All the actions taken place from these dialog box push-buttons
are related to both models (i.e. red TARGET and generic CAD)
and they are performed in a particular view (a screen viewport)
similar to front-view; whilst the remaining views used for
facade's multi-views visualisation.
This dialog box is divided in three parts: The first is devoted to
the Automatic procedure, the second to Manual enhancements
and the third to some useful Utilities like "Delete All
Elements", "Unload Application", "set Camera data-file", "set
Facade data-file", "place Red TARGET model" and so on.
Interfaces are designed to carry on a continual interactive
dialogue for current values concerning virtual camera's exterior
orientation so that the user is informed of actions in progress at
each step. This is particular important for feedback purposes.
Good diagnostics and error messages are designed to help
determine the cause of an error.
The figure 2 demonstrates the dialog box used to control the
process.
S. A CASE STUDY - PRACTICAL EXAMPLE
The developed CAD-based method has been verified practically
on a neo-classical historical building. This building, built in
1890, is situated in Kozani-Greece and the rectification
parameters, of an available facade's photograph, are known by
analytical methods. These parameters’ values as well as the
corresponding values calculated by the proposed CAD-based
rectification, were used in a cross-reference test concerning the
length of two perpendicular facade's edge-distances.
From an existing documentation an orthogonal and planar
facade's part found having the wide-edge=7.5 m and the height-
edge=2.8 m. Using Adobe's Photoshop 3.0 and the available
photograph of the facade, the image co-ordinates of this part's
four corners, in pixels, were found as (x/y): 92/153, 373/221,
373/348, and 88/311.
Figure 3. Red TARGET Model and Generic CAD Model at
initial state before Rectification.
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Figure 2. The Dialog Box used to control Exterior
Orientation Rectification.
As visual display unit-VDU a 17' screen has been used and a
resolution 500x500 pixels was defined for the view where the
camera's position approximation procedure was performed.
The design file settings/working units were in m, cm and
positional units (pixels) with resolution:1m=100cm=1000pu.
Initially the virtual camera was at the ideal position just over the
facade, with co-ordinates: X0=0.0, Yo=-14.0 m, Zo = 0.0 and
camera constant: c=50 mm [Fig. 3]. Using the automatic and
manual approaches described in chapter 3 the final best fitting
virtual camera position, for the particular photo, found as: Xo=-
9.78 m, Yo=-11.36 m, Zo=-3.19 m, with the angular orientation
parameters as: w=12.71 degrees, p=40.32 degrees, x=-8.18
degrees. The camera constant, of the visual camera producing
this coincidence, found as: c=64.1mm. (FoV=36.6 degrees).
On figure 4 facade's TARGET and CAD models are displayed
as they are just after the first step of the automatic procedure.
On figure 5 the models are displayed as they are in a middle-
procedure state, and particularly after the second step of the
automatic procedure. On figure 6 both models are displayed in a
coincide state achieved by the end of the CAD-based
rectification.
All the values are related to following XYZ co-ordinate system:
Z-axis
Y-axis
zz X-AXiS
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B5. Vienna 1996
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