In the field of geometry compression, two main compression targets exist. One is triangle connectivity data and the other is vertex position data. In this paper, we propose a novel algorithm to compress the vertex data. A fundamentally different approach we took in this paper is to transform the vertex positions to the model space, a coordinate system formed by the three previously processed vertices. Once all the vertices are transformed, we found that the result shows a strong tendency to cluster around three points. We exploit such tendency during the vector quantization steps to increase the compression ratio. According to the experiments performed on 12 models, the average compression performance of our algorithm is 6.7 bits/vertex, which is a clear improvement over the previous methods.