International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B7. Istanbul 2004 
Where X,, Y, image coordinates and X, Y ground coordinates. 
One of the main goals of this study is to evaluate the accuracy 
of very high-resolution data using 2D image transformation 
method. For this aim, Ikonos and QuickBird image were firstly 
assessed using Ist and 2nd order polynomials with 10 and 20 
GCPs respectively. Table 2 shows the results of Root Mean 
Square (RMS) errors of the ground control points, which were 
formed using GPS measurement results. Although 45 well 
defined and distributed ground control points were observed by 
means of the rapid static GPS measurement, the GCPs which 
had the best distribution and minimum error factor among all 
were chosen for geometric transformation (Figure 2 and 3). As 
can be seen in tables, the RMS errors are being decreased with 
an increase of the order of transformation. 
  
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2e Ist degree 2nd degree 
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Sof GCI RMS(m) RMS(m) 
9 1.66 
lkonos 18 2.65 1.35 
ag 9 0.91 
QuickBird 18 2.83 2,57 
  
  
  
  
  
  
Table 2. RMS errors calculated by using with GPS 
  
  
  
  
  
Figure 2, GCPs observed by GPS measurements in QuickBird 
image. 
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Figure 3. GCPs observed by GPS measurements in Ikonos 
image 
As a next phase of this study, the GCPs were collected by using 
hand GPS measurement technique for the same goals. In the 
next field measurements because of the bad weather conditions, 
the same GCPs which were collected by GPS before were not 
reached. Only the 18 same GCPs were used in this evaluation 
phase. It was again seen that the higher order of transformation 
the better RMS errors obtained (Table 3). 
  
  
  
  
  
Ist degree 2nd degree 
# of GCP RMS(m) RMS(m) 
9 7.48 
Ikonos 18 8.94 6.57 
Re 9 10.48 
QuickBird 18 14.36 11.40 
  
  
  
  
  
  
Table 3. RMS errors calculated by hand GPS 
In the last phase of the analysis, the digitized 1/5000 scale 
orthophotos were used to collect GCPs. Only 6 GCPs from GPS 
were able to be determined over the orthophotos because of the 
date factor. 24 GCPs were selected from the 8 digitized 
orthophotos which cover the study area. The transformation was 
evaluated using with 10 and 24 GCPs respectively. Table 4 
shows the RMS errors calculated from the Ist and 2nd order 
transformations.