ance with the reference model. The position of reference model 
for this experiment is shown in Figele 
  
2) ~ 32 mm 
d. 
20 — 32 mm 
[:] 
[-] 
[] 
eee 
3 0 E17 4-1 
1: 
  
  
  
Fig. 2 
The simplist method to be used is to regard the whole block 
as an area with constant systematic errors, all models in the 
whole block are superimposed on an unified reference model, 
situated within a small square with tie points as centers and 
sides length of 20mm, mean values for residuals of tie point 
coordinates are computed, such values with reversed sisns will 
act as corrections ,r systematic errors for the tie point. 
2. Statistical check on corrections for systematic errors 
at tie point 
After obtaining corrections for systematic errors at tie 
point, a statistical check has to be made in order to con- 
firm whether significant systematicness exists or not, here 
T-testing was used, its mathematical formulae are /1/ /5/ 
rx (ys /A/ 
where K refers to the number of sub-blocks 
ng is the number of model points within the ith sub- 
block 
IA is the absolute value for the mean value of the 
residuals within the ith sub-block - 
RMSE is the root mean square error of residuals of photo 
coordinates in blocks 
When T <1 (corresponding to significance level (0.15, 
n => 60), E(Ai)=O0, that is, no siznificant systematic error 
exists, hence it is not necessary to make a posteriori | 
- 491 -