Full text: Proceedings, XXth congress (Part 8)

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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B-YF. Istanbul 2004 
2.1 Experiments 
In order to estimate accuracy of card size digital cameras, 
experiments were performed using 7 kinds of card size digital 
cameras. Figure 3 shows these cameras and Table 1 shows the 
major components for these cameras. Stereo images were taken, 
and camera calibrations were performed by the resection 
method using 9 control points. After the camera calibration, 
accuracy was estimated using R.M.S.E. for 33 check points. 
Test target were made by the accuracy of =0.01lmm for plane 
coordinates and 0.5mm for vertical. Figure 4 shows the test 
target. 9 out of the 42 points on test target were used for camera 
calibrations, and other 33 black points were used as check 
Stereo images for the test target were taken five times with each 
camera under the same condition (distance from the center of 
camera to test target, length of base line), and image 
coordinates for each point were given as the center of area 
gravity by image processing. Accuracy for 3D coordinates of 
check points was compared with space resection using 9 GCPs. 
The average accuracy for 3D coordinates of check points were 
investigated in this paper. 
pscri DSC 
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DiMAGE Xt - 
Figure 3 Card size digital cameras 
Q : Control Points 
Q : Check Points 
360(mm Ya € à 
Figure 4 Test target 
2.2 Evaluation of Lens Distortion 
In order to estimate lens distortion for card size digital cameras, 
three different lens distortion models shown in Table 2 were 
investigated. Model 0 means no correction for lens distortion, 
model 1, 2 consider only radial symmetric distortion, and 
model 3 considers both radial and tangential distortion (Fryer, 
Figure 5 shows the R.M.S.E. for 33 check points by each lens 
distortion models, and R.M.S.E. for the other amateur digital 
cameras with more than 3 mega pixels are shown together. It 
may be seen from the results that lens distortion for the 
armature digital cameras are improved by radial polynomial 3rd 
degrees distortion model (Model 1), and model 2 and model 3 
do not show any further significant improvements compared 
with modell. 
Similarly, R.M.S.E. for some card size digital cameras are 
improved by modell. However, R.M.S.E for some card size 
digital cameras are improved remarkably by Model 3. It may be 
said that the reason are depend on some mechanical problems in 
downsizing and lightening process such as lens storage 
mechanism and multi-layer structural lens, and individual 
problem of the specific card size digital cameras. Therefore, it 
can be said that lens distortion for the card size digital cameras 
should be corrected by using radial and tangentral model, 
instead of lens distortion for the armature digital cameras can be 
corrected sufficiently using radial polynomial 3rd degree model 
as usual. 
2.3 Relation between image resolution and accuracy 
The relationship between the image resolution and accuracy is 
shown in Figure 6 and 7, and the results for armature digital 
cameras are shown together. Figure 6 shows the R.M.S.E for 
the both camera groups corrected by Model 1. Figure 7 shows 
the R.M.S.E. for armature digital cameras by Modlel, and 
R.M.S.E. for the card size digital cameras corrected by Model 3. 
It may be concluded from these figures that the significant 
accuracy are achieved in the case of digital card size cameras 
when lens distortion are corrected by model 3. 
Table2 Lens distortion models 
Model No Correction item Equation 
0 No correction. 
: ; > dx=krx 
1 Radial distortion ; 
à - dx = kr x + karly 
2 Radial distortion 2 : 
dx = kr xe kn £2x! )+ ky 2x0 
3 Radial and tangential distortion de ky kn 42 2x 
Where, d, and d, : correction value,Æ, ,k; and k; :distortion 
. . 2 2 2 
x and y : image coordinate, r” =x" +y 
Table 1 Major components of the card size digital cameras 
Producer [Product Name Number of Pixel CCD Sensor Size (WX H x D) Weight 
(Mega pixcel) 
CASIO EXILIM ZOOM EX-Z3 9.20 1/2.5 inch 970x570x229 mm 126g 
MINOLTA |DiMAGE Xi 3.20 172.7 inch 84.5 X 72.0 X 20.0 mm 130 
MINOLTA j|DiMAGE Xt 9.20 1/2.7 inch 85.5 x 67.0 x 20.0 mm 120g 
Canon IXY DIGITAL 30 3.20 1/2.7 inch 85.0 x 56.0 x 23.9 mm 165 
PENTAX  jOptioS 3.20 1/2.5. inch 83.0 x 52.0x 20.0 mm 98 
SONY cyber-shot DSC-F77 4.00 1/1.8 inch 92.6x 71.0x 27.0 mm 152g 
SONY cyber-shot DSC-T1 5.10 1/2.4 inch 91.0x 60.0x 21.0 mm 155 

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