International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV. Part B5. Istanbul 2004
The second phase consists of detailed geometric documentation,
such as: floor plans, facade appearance, sections and similar, all
in digital vector form, by using appropriate CAD tools. Since
this phase is the most expensive and the most complicated part
of documentation production, it is not compulsory.
Division of procedures into two phases enables the first one to
be performed in campaign manner (by object groups,
environment entities or some other criteria) for relatively short
time and with relatively limited financial resources. The goal of
this phase is preventive capture of information about cultural
object, because present object condition is ?frozen? at the
moment of making documentation. At the same time, this is
prerequisite for the second phase to be performed at any time
afterwards without any danger of loss of information. The most
important elements of suggested procedure will be explained
further on in this paper.
5.3 Image capturing plan
The successful realization of mass technical documentation
production demands certain preparation. This preparation
involves inspection of object of cultural importance and
determination of the target objects for each campaign. The
disposition sketch should be made and it should serve as the
basis for image capturing plan, as well as for checking of all
critical elements for planning (visibility, estimated maximal
extent of images in height and width, etc). Beside the data
collected at the field, some other information sources are
important for image capturing plan (photographs, cadastral
maps, etc). Image capturing plan should contain approximate
disposition (position and orientation) for all planned images
(Figure 1).
6 à
5.4 Image capturing
Figure 1: Image capturing plan
Suggested procedure assumes imaging with Rolleiflex 6006
color film camera (Figure 2). Images are taken by hand, from
the ground or by moveable telescope crane. Imaging has all
campaign characteristics. After short preparation (photo
signalization of control points), imaging is done according to
previously created plan. Films are developed after finished
campaign or at the end of the day. At least one color contact
copy should be made for each photo. Right after, it should be
evaluated whether imaging plan has been satisfied. Image
copies are used also for the selection and notification of control
pointa during following phases.
Figure 2: Original image made by semi-measurement camera
Rolleiflex 6006
5.5 Image scanning
Suggested procedure assumes scanning of photogrammetric
images directly from negative by using desktop scanner Epson
Expression 1600. Although it is not difficult to calculate
appropriate resolution for each concrete case (Chong et al.
2003), it is recommended to do scanning in resolution 1600 dpi,
full color. Namely, it was determined empirically that 1600 dpi
is the resolution that corresponds to the limitations imposed by
amateur color films and standard procedures of photo laboratory
processing.
5.6 Geometric rectification of images
After scanning, it is necessary to geometrically rectify images,
i.e. to eliminate errors introduced by image capturing, photo
processing and scanning (Figure 4). Geometric rectification is
based on theoretical values of image coordinates for grid points.
These points are copied onto film during image capturing -
'resau' plate is built on Rolleiflex 6006 camera (Figure 2).
Collocation by least squares, with previous affine
transformation for trend elimination is proposed mathematical
model for geometric rectification. Example of systematic errors
typical for camera Rolleiflex 6006 and scanner EPSON
Expression 1600 is shown at Figure 4. For further processing
only geometrically rectified images are considered.
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5.7
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