For a varity of reasons GIS users often want to exchange data. Often GIS software develop by private software companies store data in a proprietry format proteced by copyright. In general one companies software may not read data in the format of another piece of software from a rival.
Whilst some software companies have opened their standards to the public(ie. ESRI) others have not. When it is not possible for software to read data in another format it is possible to exchange data througth a neutal software, the SDTS is one of these formats.
Target one will encode data into the format, this is then transmferred to the target who reverse the process so the data is readbale by thier own software.
The SDTS is one of these formats, and provides for a comprehensive range of features within the standard, including raster data and vector data.