The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008 
rectifided image with RPCs, DEM and GCPs. For ortho- 
rectified image produce, the RPCs has to effect to change the 
distance depending on height. (See Figure 6) 
Figure 6. Height influence according to different height. 
Figure 7. Generated ortho-rectified image using RPCs, GCP 
and DEM 
We also tested ortho-rectified image, the step of ortho-rectified 
image is as following 
Step 1: Open a FIR product using commercially available 
softerware (PCI, ENVI) 
I ENVI S/W was used 
Step 2: Select RPC tool and read K.2 RPC file 
! The RPC has different denominators with 3rd-order 
polynomial from KOMPSAT-2 
* Step 3: Refined RFM with GCPs ; choose different Z values 
for each GCP: check if RMS is consistent with the true Z error. 
Used GCPs number for refined KOMPSAT-2 is 8 points and 
90m SRTM DEM was used to ortho-rectified image. The 
generated product is Figure 5. To evaluate ortho-rectified image 
by RPC, we compare the resulted direct sensor model with RPC 
result. 
In Figure 6 and Figure 7, it is possible to use KOMPSAT-2 
RPC instead of KOMPSAT-2 DSM for 3D processes like ortho 
rectification, stereo restitution or correlation. 
4. CONCLUSION 
The KOMPSAT-2 geometric accuracy verification was 
successfully evaluated from 2007 through 2008. The 121 test 
sites provided excellent condition for geometric verification due 
to its flat terrain and a very good grid infrastructure. 
This paper investigation is to check and verify the geometrical 
performance when KOMPSAT-2 images data with precision 
orbit data, precision attitude data are employed and briefly 
introduce the direct sensor model and rational function model of 
KOMPSAT-2. The ephemeris, attitude, time and image data 
from KOMPSAT-2 acquired and direct sensor model or RFM 
could be met 51.65m (CE90) geometric accuracy on the flat 
ground. For the future research work, we should continue the 
calibration and validation of KOMPSAT-2, after KOMPSAT-2 
Cal/Val Phase II, more excellent and accurate results can be 
come out. 
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