Applicability analysis of seven-parameter coordinate transformation model

The seven-parameter transformation model of Bursa and Molodensky was illustrated in the paper.The correlations among parameters of shift,rotation angles,and scale in seven-parameter transformation model were analyzed.And this paper also researched the influence of transformation parameters when the known coordinates change slightly.The low correlations among the seven-parameters were testified when the transformation model was applied to a small region,the small change of known coordinates had a large effect on transformation parameters,but it was small for Molodensky model,the Molodensky model was more stable than Bursa model.The equivalence of the two seven-parameter models in a small region was also testified.Finally it was found that Molodensky model would be more applicable especially in a small region.