The plugin helps to get the right dimensions for your model in Blender. The way it works can be explained by the following usage scenario:
- Import an OpenStreetMap file that covers the area relevant to your model
- Mark the target edge on the imported OSM object that corresponds to a specific edge of your model
- Mark the corresponding edge on your model
- Scaling will be applied to your entire model, so the length of the marked edge of your model will be equal to the length of the marked OSM edge
Download link and documentation are at my github account: