Honam Lee 
  
4 TEST RESULTS 
93 GCPs were used, but five were removed as considering blunders. These GCPs are known to have a determination 
RMS error of less than 1 meters in planimetry and height, but identification errors could add another 20 or 30 meters, 
because we used the geodetic control points in the mountain as GCPs. The summaries of the test results were given in 
Table 2 and 3. 
  
  
  
  
  
  
  
  
  
  
  
  
Amount RMSE(m) 
Test Area Check GCPs Check Points 
GCP | Points X Y H X Y H 
I 18 18 2.86 4.37 6.44 4.89 5.28 8.36 
II 18 16 3.67 1.97 4.14 5.38 3.68 7.39 
III 16 17 2.18 3.62 4.23 3.87 4.48 7.22 
IV 16 18 3.06 2.85 4.01 3.28 2.22 5.15 
V 20 20 3:27 2.35 4.01 3.62 4.97 7.48 
  
  
  
  
  
  
  
Table 2. Test results with analytical plotter 
  
  
  
  
  
  
  
  
  
  
  
  
Amount RMSE(m) 
Test Area Check GCPs Check Points 
GCPS..|- points X Y H X Y H 
I 18 18 33.46 39.82 43.67. 38.32 45.72 47.36 
II 18 16 33.34 37.67 29.45 35.47 42.34 39.38 
III 16 17 29.98 34.22 31.99 32.43 35.49 46.54 
IV 16 18 32.45 40.21 28.38 43.23 36.71 52.38 
V 20 20 37.16 38.39 48,26 38.97 48.28 55.69 
  
  
  
  
  
  
  
Table 3. Test results with digital photogrammetric workstation 
5 ANALYSYS AND CONCLUSIONS 
Using approximately sixteen well-spaced geodetic control points per model, all segments showed RMS error just below 
the pixel region at check points in analytical instrument. This result showed that only identification errors were 
introduced because test were done using the geodetic control points that located in the top of the mountain as control 
points. In case of DPW, half of the ground controls could not found or distinguished when we displayed the image on 
the monitor. 
It presented that the RMS errors with DPW test was fluctuated case by case. And the magnitudes of the errors were 
reached more than three pixels. Due to the lack of image interpretation capability in image product comparing with film. 
It showed that the geodetic control points is not suitable as the ground control points in DPW for modeling the SPOT 
image. The RMS errors for the 88 GCPs which modeled at analytical plotter were about 2-5m in planimetry and 5-8m 
in height. The RMS values for the same number of GCPs at the DPW were about 32-45m in planimetry and 39-55m in 
height. 
If the results in this study can be verified by further experiment, the method presented here may be profitably and 
reasonably applied to GCP acquisition, map revision and thematic mapping with SPOT image for the developing 
country. The test result revealed that geodetic control points can be sufficiently used as ground control point in 
analytical plotter. But, problems may occur in the case of digital photogrammetric workstation due to the lack of 
interpreting and finding the conjugate points for geodetic control point on mountainous area. 
The results presented in this topic have also proved the feasibility of applying the analytical plotter to locate the GCPs 
with subpixel accuracy for SPOT images by manual interpretation of geodetic control point in the film product. But, the 
positional accuracy of the GCP heavily depended on the experience and performance of the operator. So, automatic or 
semi-automatic technique, which can be used to locate the GCPs for higher accuracy than the manual method in digital 
environment should be studied in the future. 
  
532 International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B3. Amsterdam 2000. 
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