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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 
After UAV has landed, GPS onboard should be switched off 
immediately, otherwise the GPS data will be lost. It is due to the 
limitation of GPS log file memory. The same been applied for the 
next flight mission. The operator is in charge of downloading all 
of the images from the digital camera and the GPS log file from 
the autopilot chip. 
2.2 Camera calibration 
Camera calibration was carried out to determine the 
parameter of the camera that is used for image acquisition. These 
parameters are required for interior orientation during image 
processing using photogrammetric software. In this study, self 
calibration bundle adjustment was carried out before flight 
mission. Plate calibration which has a dimension of about 0.6 
meter x 0.6 meter and consist of 36 reflective target with various 
height were used in camera calibration. During the calibration 
processes, the camera captured eight images from different angle 
of view. This is known as the convergence method in 
photogrammetric work. The distance between camera and 
calibration plate is approximately the same. The images taken 
were processed in calibration software which is known as 
Australis software. Australis software requires the size of pixel, 
number of horizontal resolution and number of vertical horizontal 
of the images. Finally, this software will automatically produce 
parameters of the camera. Residual of bundle orientation after 
camera calibration reached sigma0 is 0.681um. Root mean square 
(RMS) of image coordinate is about 0.27 um. The result of the 
camera is shown in Table 1. 
  
  
  
  
  
  
  
  
  
  
  
Camera Parameters | Standard Deviation 
c (mm) 1.006e-002 
X, (mm) 1.006e-002 
Y , (mm) 4.133e-003 
Radial(K,) 2.135e-004 
Radial(K;) 7.459e-005 
Radial(K3) 8.340e-006 
Tangential(P,) 3.526e-005 
Tangential(P;) 3.198e-005 
Affinity (B,) 1.085e-004 
Scale Factor (B;) 1.211e-004 
  
  
  
  
Table 1. Camera Calibration Results 
There were three set of camera calibration bundle that were 
computed to ensure the consistency of the result for parameters. 
Based on three experiments, we choose the best results by 
referring to the sigma0 values. The results obtained from camera 
the calibration were required in the interior orientation during 
image processing. 
3. IMAGE PROCESSING 
The UAVs images will be processed in photogrammetric 
software. In this study, Erdas Imagine was used to process all 
acquired images. All UAV images will be saved automatically in 
jpeg file and it will usually cover the whole coverage of the study 
area. Normally, photogrammetrist requires at least three or four 
ground control points for each model. Ground control points were 
established using GPS observation by either real time kinematic 
or rapid static method. However, the capablities of onboard GPS 
provide an opportunity for photogrammetrist to use the data for 
image processing. This study will compare a result between 
495 
image processing by using control points from Google Earth 
coordinates and image processing by using GPS onboard. This 
study will also propose a new method in image processing by 
using GPS onboard data. 
3.1 Proposed Image registration 
Image registration is required for exterior orientation process 
in photogrammetric software. We propose a new image 
registration method that uses the onboard GPS as a primary 
control points for stitching of the UAV images. This registration 
was carried out to evaluate the initial position of photogrammetric 
product based on the onboard GPS . 
  
  
F3 Fi 
O © 
x. JN 
Ré Fx. Fy, 
x’ ^ 
p (9 OQ E 
  
  
The principal point (Fx,, Fy,) is the origin of image. The 
coordination of the onboard GPS also orthogonal with the 
principal point coordinates due to the position of GPS which is 
placed vertically above the camera. Therefore, coordinates of F;, 
F,, F;, and F4 can be determined by using number of horizontal 
pixel, vertical pixel and size of pixel. Coordinate of F;, F? F4 and 
F, can be used in image processing as control points for each 
model. The fiducial points can be expressed by equations for Fy, 
and F;, as shown in Equation 1 and 2. 
Fix) = Fx, + (Hp/2 - 2) Sp +€ (1) 
Fig) = Fy, + (Vp/2- 2) Sp + € (2) 
Where Fx, and Fy, = origin coordinate of the image which is 
obtained from GPS onboard 
Hp = number of horizontal pixel 
Vp = number of vertical pixel 
Sp = pixel size of image 
€ = rotation error 
The Equation 1 and 2 are represented in matrix form. 
Hp 
(Feo). Io (Sp«(9 (Q9 
"CR 
The exposure location of an aerial photograph, an object point and 
its images on the image plane are all on a straight line. Therefore, 
collinearity condition equation must be applied in Equation 1 and 
2 to eliminate rotation error (Paul and Bon, 2004). There are three 
rotations involved in this equation; omega (o), phi (b), and kappa 
(K) rotations. The rotation errors are the effect of air turbulence 
during flight mission due to the wind correction. The Equation 1 
and 2 after rotation correction are shown in Equation 4 and 5.