SPANS binary format (TBB/VTX)

GDB supports the SPANS vector binary format files (top/vtx) for reading only. The binary point and table files (tbb) are supported for reading and writing. Where the vector layer has attributes in a tbb file, the attributes are also opened when the vector layer is opened. The vector layer may be opened by selecting either the top (topology) or the vtx (vertex) file. If the tbb file is selected from a top/vtx/tbb set, then only the attribute (tbb) portion is opened.

In SPANS a vector file set appears as one layer. In GDB the separate topological layers are shown. That is a topological arc layer is shown as a node layer and an arc layer. A topological area layer is shown as a node layer, an arc layer and an area layer. When a topological layer is opened, the nodes are shown by default.