The system must be easy to operate, not only from the
point of view of communication with program, but also
from the point of view of stereo-operation. One of the
basic problems here would be free selection of the most
proper floating mark control coordinate system. The
following coordinate systems can be here distinguished
for our purpose: the spatial fiducial coordinate system,
the leveled spatial fiducial coordinate system and the
above system after transformation to parallelity with the
field coordinate system (but keeping not changed the
name of axis closest to the camera axis - this would
assure the model depth control connected all the time
with identical mouse key or other generator of impulses,
e.g. P-cursor). The operator of the system should have
also approach to the special temporary coordinate
system, which being defined „on purpose” would suite to
ease the operator's work (e.g. the coordinate system
parallel to the tilted facade, or polar coordinate system
which fits a dome parameters, [Jachimski 1975] etc).
The system must be easy to operate also from the point
of view of plotted documentation peculiarity. Historic
buildings, and other buildings even more, have many
repeatable features: windows, door, ornaments etc. The
HMDW system can and should be equipped with
subroutines which will allows to build a pattern for each
building repeatable feature and with a system which will
allow for an easy implementation of repeatable elements
spatial representation to the historic monument digital
model created in the computer memory (such a system
would be also used to build and implement conventional
signs on maps, if map production would be occasionally
performed eg. for historic urban studies).
Usually historic monuments are plotted with the use of
several stereopares, which partially overlap each other. A
vectorial monument evaluation portions taken from
adjoining stereopares should match each other in double
recording strip. To ensure the full awareness of matching
actions undertaken by operator, the HMDW system
should provide simultaneous observation of both
matched stereopares along the overlapping strip. The
floating mark being operated in selected fotogrammetric
coordinate system connected with one stereopare is
automatically properly located also on the second one via
field coordinates of its position. The operator can decide
about the optimal evaluation of a detail analyzing
simultaneously matching of vectors with both spatial
images.
To create conditions for the simultaneous plotting of
overlapping areas, the system must use the screen
splitted to four portions. In most cases it would be
convenient to have it split vertically again (eg. for plotting
a building corner from two perpendicular stereopares).
Sometime, however, the overlapping zones will be
horizontal rather than vertical and for that cases the
screen must be split to the regular four quarters. With
hon-scrolled images and dynamic floating mark such a
multipurpose split-screen operation is possible even on
standard PC-s.
The overlapping zones matching function create an
peculiar observation environment which can be used also
when multi-image control points survey is concerned
during preparatory terratriangulation stages. Up to four
pictures matching portions can be surveyed simulta-
neously. In cases when there is more than four over-
lapping pictures, the operator can select one of them as a
reference picture, and can visualize remaining 3 pictures
262
sets one after the other, keeping the reference picture on
the screen.
The results of control points multipictorial identification
should be marked on the pictures (artificial temporary
sygnalisation - similar to pinholes made with PUG on
photographs - but non destructive for the digital image),
to create pass-points for further processing.
Use of standard PC-s is limiting to certain extend the
broad survey automatisation, specially when it is
understood as a mass survey procedure. For selected
terratriangulation points though, and in some other
monument evaluation cases an automatic correlation
subroutine would be very advisable. It would be
implemented as two or three independent functions
constructed with the use of different algorithms, just to
use more developed but more time consuming ones only
in the most difficult matching cases, while other points
would be autocorrelated with the faster but less
sophisticated subroutines.
Except of autocorrelation procedures there is another
possibility of semi automatization by automatic
evaluation of edges of contrasting image zones which
would be hand-indicated by operator. That method
provides a high subpixel accuracy of line location on
digital image [Streilein 1992, Jachimski 1992a], and
could be used for semiautomatic control-point survey
when they are defined as a two lines section. If fast
enough, that type of subroutine could be used also as an
semiautomatic tool supporting plotting (for that purpose a
less dens line automatic analysis would give sufficient
accuracy in a shorter time).
The proper vectorial representation of a monument
selected lines (edges) can supplement a photoplan of
facade or other decorated surface of the object. Also
photoplan portions can be implemented to fill some
Zones of vectorial representation, where the monument is
densly decorated or has many very small details which
do not necessarily need vectorisation. To build such a
mixed representation of a monument, one could use
another program for differential rectification of images.
On the other hand the resampling itself it is an easy
subroutine. It would be probably much more difficult and
time consuming to transfer rectification control data from
HMDW to other system, just to produce resampling, and
then to transfer photoplan again to HMDW to merge it
with the vectorial representation, than to build all the
product stages in one system. Therefore we consider
HMDW as a small workstation which can be used also
for rectification of selected portions of images. The
advantage coming from such a solution would be also
great when more complicated rectification in spatial
projections are performed (egs vault, dome).
3. CLOSING REMARKS
An as found recording team, or just the monument
revitalisation team which prepares monument recording,
all of them would profit from a flexible use of
photographic pictures during monument evaluation to
produce some inventarisation documents. The broad use
of photogrammetric methods would be beneficial only
when it does not require big investment and long training.
A small digital stereo plotter which incorporates several
other useful functions could be an excellent toll for such
applications, but it must be operated with user friendly,
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B5. Vienna 1996
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