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3.2. Setting Control point Targets
As an object for this experiment, control point
targets on a wall in a room and the target area
is 3m (L) x 3m (W) approximately.
For the control point allocation and the target
shape, see fig. 6. Total of 56 targets were set
on the wall with the depths of 4 steps ( wall
surface, 12.5cm, 25cm and 50cm) being fixed on
the wall by attaching aluminum bars onto the
bolts on the wall surface.
Fig.6 Control point Allocation and
the Target Shape (Full size)
3.3. Metric Camera
PENTAX PAMS-645 was used for taking pictures.
The camera is a terrestrial photogrammetric
camera of fixed focus length and has four
fiducial marks, vacuum system, etc. Interior
orientation of the camera is calibrated and
corrected photo coordinates based on the data
sheet attached. In this experiment, the camera
was used, attached to the telescope part of the
transit for IMS by using an adaptor.
3.4. Determination of Exterior Orientation
Parameters
Procedures to obtain exterior orientation
parameters are shown as following order:
(1) By using the IMS system, determine the
positions of transits on the right and left
hand sides and measure the control point
target accurately.
(2) At the measured control point targets, take a
photograph almost vertical against the wall
with the camera attached to the transit, give
orientation of single photograph thorough
positions of the transits and collimating
angle as initial parameter and obtain the
correcting values (AX, AY, AZ, Aw, Ag and
Ax) of positions and tilts of transit and
camera. Keep this relation between the
transit and the camera after this.
(3) Collimate a target around the center and take
a stereo photograph.
(4) Obtain the horizontal angles (4) and the
vertical angles (o) of collimating
direction of the transits by calculating
three coordinates (as shown in fig. 7) of
the transits on the right and the left
hand sides and the target.
(5) Determine the exterior orientation
parameters from the correcting values and
the actual measured values.
(6) Divide the exterior orientation parameters
into relative and absolute orientation
parameters and converts them into the
orientation parameters which are necessary
to the stereo image workstation.
Target area
Target
ec x, Y. 2)
> X
ST!
(X01, YO1, Z01) ST2
(X02, Y02, 202)
Fig.7 Orientation Processing by Using the IMS
3.5. Experiments Results
Results of 3D measurements by the
conventional orientation procedures (case A)
and the IMS orientation procedures (case B).
are described below. Also, even in the
conventional orientations, the camera
positions and angles, obtained by the IMS,
are used as approximate values.
[Parameters]
® Camera arrangement:Convergence photography
€ Focus length of camera : f=44.979(mm)
® Length for camera and object: H=3 (m)
€ Base-line length for cameras: Bz1.5m
Assuming coordinate measuring accuracy of the
stereo image system (resolution) : op=7 (um),
measuring accuracy of coordinates in 3D
measurement can be obtained by the following
formulas:
[Theoretical value of plane coordinates]
H
gXi= dy = TA op = 0.467(mm)
[Theoretical value of depth coordinate]
H H
gZ = >: = op = 0.934(mm)
