2. PHOTOGRAPHY SYSTEM
2.1 CAMERA
We chose Nikon F-801 as the camera for loading. This
camera is small-size and the radio-control photography is
possible. In addition, there are self-timer, auto-winding
equipment, and function of exposure compensation etc. and
roll-film is used. About camera lens we attached a
wide-angle lens of focal length 35mm by considering the
economical efficiency of photographing area. As the camera
is non-metric camera, we manufactured fiducial mark plate
that the cross mark was engraved on plane glass of about
0.2mm thickness and then attached it just in front of film.
And, after exacting radial and tangential lens distortion
coefficients and correcting PPA(Principal Point of
Autocollimation), PPS(Principal Point of Symmetry) and focal
length, we made into semi-metric camera(Oh, 1992).
2.2 RADIO-CONTROL SYSTEM
We manufactured the airplane for radio-control to be able
to take off and to land at the object area that the
geographic information required directly by considering
stability, formness and convenience of transport. And we
installed gyro, so that the camera may be maintained
vertically regardless of the rolling of airplane. We
manufactured the equipment for minimizing the shake of
camera by the vibration of airplane engine. And we installed
the type to get out of attachment as the loading equipment
of camera. As for the model of radio-control airplane we
used the airplane of which the wing length is 180cm, the
body length is 90cm, the engine is 4 cycle, the weight is
2,800g(state that camera was loaded) as PIPER CUB type
and the used radio-control equipment is 7-channel(Kang,
1995).
MCORESIT
Figure 1. Radio Control airplane
About the developed R/C system we examined all the
matters such as the flight stability, the control state of flight
altitude, and the speed control state of radio-control
equipment, the balanced nature of airplane, the function of
rom control of engine, the motion state of servo, the control
state of camera, and the stability of take-off and landing
etc. over several times and examined the features such as
the image sharpness, the image resolution attendant upon
the exposure degree of film, the shutter speed and the open
state of f-stop etc.
As the result, for the optimum flight condition wind
velocity was below about 5m/sec. And the flight altitude
that the flight control was possible with naked eye is within
about 400m. And as for the runway the open land of
432
about 5m x20m was necessary. But it was better
according as it is wide. For the prevention of shake of
image by flight speed and engine vibration it was desirable
to photograph by making the speed of camera shutter more
than 1/500sec and making the open of f-stop of camera to
considerate the depth of field more than f/11. And in
accordance with this about the photosensitivity of film it
was profitable to use ASA 400 slide film. Photography time
was proper from 10:00 am. and 2:00 p.m.
3. ACCURACY MEASUREMENT
3.1 PHOTOGRAPHY
So as to examine the accuracy of acquired geographic
information we photographed by arranging 88 ground object
points with the lattice type of 30X 30m interval on the
open land and changing into 5 stages from the flight
altitude 100~400m. As for fim we used Kodak ASA 400
slide film. We photographed by trying the manual operation
in accordance with the exposure state after making the
shutter speed at the time of photography as 1/500—
1/2,000sec and by making the value of f-stop as f/11~
f/16. So as to extract the conditions such as the photo
scale attendant upon the scale of demanded geographic
information and the rate of height of base line(B/H) etc. we
photographed by changing the endlap into about 50—80%
at each flight height.
3.2 GROUND CONTROL POINT
As for the decision of 3 dimension coordinates of GCPs
this paper decided the position of one reference point
installed at the object area which was about 13km away
from the reference point in the compound of Chungnam
National University that the location has already been
decided by GPS measurement with the relative positioning.
And then about 88 ground object points we observed from
the reference point of the object area for 2 minutes
respectively by kinematic GPS. As for the observation data
we calculated 3 dimension coordinate on the coordinate
system of WGS84 by treating with SBP and MBP methods
of Trimvec-Plus software.(Park, 1992) About the calculated
coordinate we calculated RMSE by using controlling and
calculating Trimnet-Plus which is the software of network
control. The calculated RMSE is as is in the table 1.
Table 1. RMSE of GCPs by GPS(88 points)
coordinates X Y Z(height)
10(m) 0.0056 0.0043 0.0121
About the ground object points we decided the size So
that the photography may be made with about 0.03mm in
view of a film photographed at the flight altitude 300m.
We extracted the exterior orientation parameter of camera
through the bundle adjustment theory from the GCP in the
photographed film and the coordinate of fiducial mark.
3.3 ANALYSIS
About the film photographed with diverse flight height
and endlap, we calculated the 3 dimension coordinate of
ground object points and RMSE through the program of
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996
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