International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B3, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
Figure 10. Intersection image
4. EXPERIMENT
4.1 Data acquisition and camera calibration evaluation
Data acquisition was performed in our test field in order to
confirm the validity of the proposed simultaneous adjustment.
The test field had 117 GCPs, and seven GCPs could be utilized
in the triplet area. The GCPs were obtained by static
observations using GPS that were set on the edges of road
paints. Table 1 shows the data components used in this
investigation and Figure 11 shows the centre image used in this
investigation. It was taken at about 820 m and the image scale is
about 1/13,700. Therefore, the GSD (Ground sampling
distance) was about 12 cm.
Domain Item Contents
Test field All GCPs 117 points
Platform Helicopter AS-350BA
Flight Speed 120 km/h
Altitude 820 m
GPS Rate 1 sec
IMU Rate 200 Hz
Laser Scan rate 50 kHz
Scan angle 30 degree
Pulse 4 pulse
Digital Camera Focal length 60 mm
Sensor size 9 x 9 um
Image size 5440 x 4080
Color depth 16bit
Table 1. Data components
Table 2 shows the root mean square errors for seven check
points and permissible errors means restrictions for check points
that are established by GSI when generating each scale map. RA
(Relative Accuracy) means the value that was computed from
equation (7). Standard error was computed under the
56
assumption that image-coordinate pointing is accomplished
igure 11. Whole centre image
Type ox[m] | oy[m] | oz[m] RA
Proposed method 0.209 0.269 0.242 1/1963
Standard error 0.123 0.123 0.482 1/1601
Permissible error
1/500 0.150 0.150 0.200 1/2813
1/1000 0.300 0.300 0.300 1/1578
1/2500 0.750 0.750 0.500 1/699
H =820m in RA
Table 2. RMSE for check points
= 1
Jol +o} +o? (7)
2 2 2
295 3e; 3;
Ox = tn Oy = 0) Go, = —9À
ny ny n,
where H — Altitude
0x, Oy, 07 7 RSM error of X, Y, Z
Oxi, yi, Oz; ^ differences in X, Y, Z coordinates
ny, ny, nz = numbers of check points
H
Oxo "0p = = (8)
HH
20 7 V2 SA
p B."
where Oxo, Om, 07) = standard error
H = altitude
f= focal length
B = base line
op = pointing accuracy
It can be seen that the vertical coordinate value, Z, is better than
the horizontal coordinate values because the vertical
coordinates of the pseudo-GCPs are constrained by laser
distances as a characteristic of the proposed method. On the
other hand, it can be found that the relative calibration accuracy
is less than 1/500 and more than 1/1000 in comparison to the
permissible error. It is consequently concluded that camera
calibration using pseudo GCPs is practical.
4.2
Ob
in |
the
car
obt
anc
pro
sha
pro
mo
It i
sin
1/5
Th
pse
Cor
per
aer
Th
anc
Op:
Mc
pre
Th
ger
sha
Int
