I want to use the Offline Map-Matching algorithm in QGIS to match GPS trajectories with a road network. This road network layers needs to be "a clean graph following a node-edge-model, i.e. different lines should only touch other lines, never cross them." According to the help of the tool: "you can get such a clean graph e.g. by running the PostGIS function "CreateTopology". I already have a high quality road network, but this network is not recognized as Network-Layer by the tool.
Since I am very new to Postgis, I was wondering whether somebody could advise me on how to create such a topology by providing a piece of code. Or maybe anyone has another idea on how to obtain such a network layer.