International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B7, 2012 
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia 
Fix) = Xo + (Hp/2 - 2) Sp - 
  
  
pee (x) m12 F1(y)'+m13F1 (7) | 4 
m31F1(x)'+ m32 F1(y)'+m33F1(2)’ (® 
Fiy)= Yo + (Vp/2 - 2) Sp - 
m 1F1(x)'+ m22 F1(y)'+m23F1(z) | 5) 
m31F1(x)'+ M32 F1 (y)'+M33F1 (7)' ( 
Where Fx, and Fy,= principal points of the image 
Hp - number of horizontal pixel 
Vp = number of vertical pixel 
Sp = pixel size 
f = camera focal length 
m's = function of the rotation angles omega, phi, kappa 
Fl(x), Fl(y)', F1 (z)' = rotate image coordinates are 
related to the measured photo coordinates Fl(x) and 
F1(y). 
Coordinate of F?, F3 and F, can be derived by using Equations 1 - 
5. The general formula can be defined in Equation 6 and 7. 
Fn a) = Fx, + (Hp/2- 2) Sp +e 
Fny)= Fy, + (Vp/2- 2) Sp + € 
(6) 
(7) 
Where Fax and Fy, = position of diagonal coordinate x and y 
In this study, all measured coordinates were used in the image 
processing for the production of digital orthophoto and digital 
elevation model. As mentioned in the data acquisition section, all 
acquired images will be processed by using photogrammetric 
software. In this study, for each photograph three control points 
were established; One control point was obtained from the 
principal point and the other two control points were measured 
from the proposed equations (Equation 6 and 7). These three 
control points were used to rectify each photograph and all 
rectified images were mosaiced to generate digital orthophoto of 
the study area. The result of digital orthophoto and digital 
elevation model is discussed in the result section. 
3.2 Image processing based on Google Earth control points 
The second method for image processing in this study used 
Google Earth coordinates as control points. Several control points 
were captured in Google Earth and were used for exterior 
orientation in the production of digital orthophoto and digital 
elevation model. The photogrammetric product can be computed 
Digital Orthophoto d xis 
  
  
  
  
  
496 
after going through certain photogrammetric steps such as interior 
orientation, exterior orientation, aerial triangulation and bundle 
adjustment. The results of image processing by using Google 
Earth coordinates and GPS onboard were compared and analyzed 
in the discussion section. 
3.3 Data Verification 
Photogrammetric products must be verified before they can be 
used for any applications. There were 57 checkpoints that were 
randomly distributed evenly for the whole study area. Each 
checkpoint was established by using Real Time Kinematic (RTK) 
GPS which required only 2-3 minutes per control point. The 
accuracy assessment of photogrammetric product in this study is 
discussed in the analysis section. 
4. RESULTS 
The result can be discussed in two cases; first case is the 
results of image processing by using proposed image registration 
algorithm and second case is the result of image processing by 
using control points from Google Earth coordinates. There were 
two photogrammetric products produced in this study, namely 
digital orthophoto and digital elevation model. The size of image 
block for this area is about two kilometer by two and half 
kilometer where 228 images were captured during flight mission. 
Spatial coverage of one image is about 326 meter x 245 meter. 
Each overlapped images were about 60 percent and sidelap were 
about 30 percent. These results were described in Figure 4(a) and 
Figure 4(b). Figure 4(a) shows the product of digital orthophoto 
after the rectification processes by using the proposed image 
registration method. The advantage of the proposed method is that 
the images can be rectified by using diagonal coordinate which 
was defined from the proposed algorithm and improve image 
matching during auto-tie point measurements. Rectified images 
were mosaiced and digital orthophoto was created for the study 
area. Figure 4(b) shows the product of digital orthophoto based on 
control points acquired from Google Earth coordinates. 
Based on Figure 4, in graphical view, there is no difference 
between the digital orthophoto for both techniques while for the 
digital elevation model there were slight differences. This might 
be caused by inconsistency of Google Earth and onboard GPS 
coordinates used as control points in image processing. It is 
because coordinates obtained from Google Earth and onboard 
GPS has some error that need to be considered. However, the 
details on the accuracy of the assessment of both results are 
discussed in the dicussion section. 
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Digital Elevation Model 
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