chosen. Simulated data are available from 5 strips with 10-11 
models each, 8 photogrammetric points per model, camera prin- 
cipal distance: 150.00mm, photo scale: 1:30000, in order to 
ascertain the relationship between signal-to-noise ratio and 
compensation of systematic errors, pseudo-random observational 
errors with mean square error of 5, 10 and 154m respectively 
according to normal distribution have been incorporated to 
coordinates of photo points. Two sets of practical data are 
selected. One set of data came from block data of Enping Test 
Field of Guangdong Province, in the block there are 8 strips 
with 16 models each, the Whole block consists of 128 models 
with 8 planimetric and height point situated along perimeter 
of the block, 88 planimetric and height check points, 37 
height control points stabilized by 3 chains, layout of other 
19 ones act as discret points is taken. All control points 
and check points are with surface marks, camera principal 
distance: 152.06mm, photo scale: 1:35000. The other set of 
data are given from HORDORF test field of the Federal Re- 
public of Germany, the data used are available from 5 strips 
with 27-28 models each, the whole block consists of 136 
models with 6 planimetric points situated at the upper and 
lower strips respectively, 45 planimetric check points, 
18 height control points stabilized by 3 chains, i=14b, 
111 height check points, camera principal distance: 152.75mm, 
photo scale 1:6000. 
2. Experimental approach 
While experiments are performed by using simulated data, 
not only had pseudo-random errors been added, but systematic 
errors incorporated artificialy, e.g. the change of theoretical 
fiducial value to produce distortion of planimetric system and 
that of correction parameter of atmospheric refraction to 
produce deformation of height system and to render these two 
deformations mixed together, then a comparison between result 
of a posteriori compensation and those of non-compensation 
are made, So as to investigate effect on compensatione Fi- 
nally by applying practical block data, effect of a posteriori 
compensation in application to practical materials is provede 
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