The Spatial Data Transfer Standard (SDTS), also Federal Information Processing Standard 173, was designed to transfer the full range of spatial data (i.e. vector data, raster data of different models and structures). The SDTS approaches the difficult translation between different types of spatial data by defining a conceptual spatial data model, which consistof entities with attributes in real world and spatial objects in digital representation. These spatial objects are represented as modules that identify the contents of the spatial data base. It is significant to learn the details of the SDTS concepts.