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To get an unique block it is opportune
to leave the cadastral (EN) coordinates
and to go onto canonic (XY) coordinates,
referred to the axes of the mean ellipses.
The height over the ground remains as the
third Z coordinate. A dedicated computa-
tion program easily performs this tran-
aformation, as the 5 parameters of the el-
lipses are known; and gives the new XY
coordinates in the format needed for the
block adjustment with bundles.
2.3 - For the chaining observations we u-
sed an analytical Kern DSR 11/H plotter.
No correction for systematic errors was
introduced. The phocal length (Wild P31
camera) is 99.66 cm; the image size 12 x
86 cm.
The adjustment was performed with the
excellent program PATB-PC by Ackermann-
Klein [19881], with autocalibration and
automatic gross error detection. For the
El and E2 block computations, 25 resp. 14
iterations were effected. The result was
superior to any expectation, as 1t appears
from the here below schedule 2.
The Annex 2 reports the results obtai-
ned for the control points. We must point
out their exceptional quality, which shows
the perfection of all ‘the. terrain and
plant operations (fundamental net, its
densification, intersections on the con-
trols, instrumental observations, adju-
stment computations). The final accuracy
of the controls assures a centimetric ac-
curacy in the plotting.
3. - The plotting
3.1 - The above said canonic (XY) coor-
dinates cannot be used for the plotting,
except for the pairs which correspond to
the vertices MN of the mean ellipse (fig.
3). In fact, we need that everywhere the
instrumental Y axis be normal to the elli-
pse, so that the Y coordinate of a generic
point P permits to deduce its distance to
the mean ellipse, i.e. its altitude q in
the Coliseum reference (shq).Therefore we
must give a rotation © to the canonic
coordinates of each pair, before plotting
it; we obtain thus the "normal" coordina-
tes (X'Y').
We can assume a mean 0 between the na-
diral points of the two photos of the
pair. This is not quite rigorous, as we
should assume a different 0 for each point
P; but, as we shall see later, the normal
(X'Y') coordinates are only transition
coordinates to arrive to the Coliseum
coordinates, and a little variation of ©
has no influence on the final result. In
fact, the purpose of the transition (XY)
<> UO 'y'): is Only to obtain that the Y
instrumental mouvement be quasi-normal to
the monument's surface in the whole pair.
A dedicated program TRASFH1 computes
the © rotation for the central point of
the pair, and effects the transformation
from the canonic onto the normal coordina-
tes. The normal coordinates thus obtained
for the control points are used for the
absolute orientation of the pair; its who-
le plotting results therefore expressed in
its particular normal system. The observa-
tion is done in the usual way, and does
not require special modalities.
3.2 - .The last step is to transform the
normal coordinates into Coliseum coor-
dinates, i.e. to get the transition
(X*y'2')--2o. (shqp.
This is effected by the program EL1,
which:
- gives to the normal coordinates (X'v*3
a counter-rotation -90, thus reporting them
to canonic coordinates (XY);
- transforms these coordinates (XY) into
Coliseum coordinates (sq).
The third coordinate, i.e. the height
of the point on the ground, remains un-
changed in the three references (22 -
h).
The (shq) coordinates are the final o-
nes, which are employed for the graphical
or numerical representation of the whole
wall, reported onto an unique reference
Schedule 2
Sigma naught Controls Mean resid. on the controls
Block Image Terrain Horiz. Vert. Horiz. Vert.
(microns) (m) (nr) (nr) (m) (m)
E1 5.88 0.001 71 71 0.003 0.003
E2 6.71 0.001 58 58 0.004 0.003
335