We present a new geometry compression algorithm for manifold 3D meshes based on octree coding. For a given mesh, regular volume grids are built with an adaptive octree. For each grid point, a binary sign, which indicates inside or outside of the mesh, is generated based on the distance to the mesh. In each leaf cell having a vertex, a least square fitting plane is created for a localized geometry range with signs. Finally, quantized geometry information is locally encoded. We demonstrate that the octree with signs can be used to predict the vertex positions. As a result, the proposed method generates competitive bitrates compared to the current state-of-art progressive geometry coder. Our method also shows better rate-distortion performance during decompression or transmission with improved smoothness.