International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B-YF. Istanbul 2004 
  
11 bits per pixel that correspond in 2!! = 2048 layers per pixel 
contrary to the 2° = 256 layers that provide the traditional 
images with 8 bits. 
e A surveying diagram of the same area in scale 1:5000 
of the year1978of suburban region of municipality Pylaia in 
scale 1:5000. The region was selected to be suburban for 
facilitation reasons with few buildings and soft slope for a better 
accuracy achievement. For the digitization of control points the 
above-mentioned map was used. 
e The Digital Terrain Model (DTM), of which the 
digitalization step and accuracy were one meter (Ntokou K. - 
Theodorou M., 2001). 
e Finally, the coordinates of 7 points, in Hatt projection, of 
the national network were used, in order to transform the 
measurement from the GPS, which were in the projection 
system WGS'84 
3. IMAGE ORTHO RECTIFICATION 
3.1. Image ortho rectification with control points digitized 
from surveying diagram 
3.1.1. Rectification 
For the image rectification 22 points were used (13 control 
points and 9 check points) the coordinates of which were 
received via digitization of map in scale 1:5000, which it was in 
Hatt projection. The polynomial model was selected and more 
concretely Afine transformation. (Erdas, 2001) 
The RMS error for the control points was 0.4429 m, which was 
analyzed at X equal with 0.3508m and at Y equal with 0.2704m. 
Similarly the RMS error for the check points was 0.0920m, 
which was analyzed at X equal with 0.0713m and at Y equal 
with 0.0582m. 
Considered these errors bearable, the next step was the image 
resampling with the Cubic Convolution method that resulted to 
a rectified image (Tsakiri —Strati M., 1998). 
3.1.2. Ortho rectification 
The image rectification was followed by ortho rectification with 
the use of Digital Terrain Model (DTM) of the region, the 
control points and the choice of model of satellite Spot. (Mpanta 
K., Xalkidou M., Xalkidis L., 2001) 
22 points were used (13 control points and 9 check points). The 
RMS error for the control points was 0.4114m, which was 
analyzed at X equal with 0.2929m and at Y equal with 0.2888m. 
Similarly RMS error for the check points was 0.0549m that was 
analyzed at X equal with 0.0264m and at Y equal with 0.048 1m. 
Finally the total vertical error of rectified image's adaptation in 
the DTM was estimated equal with 0.356 m. 
With those errors considered bearable, the final step was the 
image resampling with the Cubic Convolution method of the 
rectified image and the production of the orthoimage (Figure 2). 
3.2. Image ortho rectification with control points measured 
with GPS 
3.2.1. Rectification 
For the image rectification 20 points were used (12 control 
points and 8 check points) that were received from 
164 
measurements, which were realized with the Global Positioning 
System (GPS). 
The RMS error for the control points was 0.3685m, which was 
analyzed at X equal with 0.1822m and at Y equal with 0.3203m. 
Similarly the RMS error for the check points was 0.0920m, 
which was analyzed at X equal with 0.0497m and at Y equal 
with 0.0774m. 
Considered these errors bearable, the next step was the image 
resampling with the Cubic Convolution method and the result 
was a rectified image. 
3.2.2. Ortho rectification 
The image rectification was followed by the ortho rectification 
with the use of digital terrain model (DTM) of the region, the 
control points and the choice of model of satellite Spot. 
20 points were used (12 control points and 8 check points). The 
RMS error for the control points was 0.3243m, which was 
analyzed at X equal with 0.1640m and at Y equal with 0.2797m. 
Similarly RMS error for the check points was 0.0962m that was 
analyzed at X equal with 0.0810m and at Y equal with 0.0519m. 
Finally, the total vertical error of rectified image's adaptation in 
the DTM was estimated equal with 0.507 m. 
With those errors considered bearable, the final step was the 
image resampling with the Cubic Convolution method of the 
rectified image and the production of the orthoimage. (Figure 3) 
  
  
Figure 2. The panchromatic orthoimage using control 
points digitized from map.