Convert SOS to DWG

Norwegian mapping data may arrive as SOSI files, but AutoCAD and many CAD handoffs require an editable DWG drawing. Converting the data makes its geometry available as CAD entities and layers; it does not automatically preserve all GIS information.

What the SOS format is

In this CAD and geospatial context, SOS means SOSI (Samordnet Opplegg for Stedfestet Informasjon), Norway’s standard for exchanging geographically referenced data. SOSI files commonly use the .sos extension and contain text-encoded geographic features, attributes, coordinate-system information, and other metadata. Norwegian mapping agencies, municipalities, and GIS users use the format to exchange map and land information. An extension alone cannot confirm a file’s format, so check its source or inspect it before conversion.

What the DWG format is

DWG is Autodesk’s native drawing format, used by AutoCAD and supported by many other CAD applications. It stores editable drawing entities, layers, blocks, and other drafting data in a compact binary file. DWG is suited to CAD editing and exchange, but it is not a GIS dataset: feature attributes, topology, and coordinate-reference information may need separate handling.

How to convert SOS to DWG

FME Form (formerly FME Desktop) is a practical desktop choice if the installed version provides both a SOSI reader and an AutoCAD DWG writer.

1. In FME Workbench, add a SOSI reader and select the source .sos file. Check that FME recognizes the feature types and source coordinate system.
2. Add an AutoCAD DWG writer, set the output filename to end in .dwg, and select a DWG version supported by the receiving CAD application.
3. Connect the SOSI feature types to the writer. Map feature types to DWG layers and configure which attributes, if any, should be written as CAD properties.
4. Preserve the source coordinate system or specify an intentional transformation; confirm coordinate units and any writer coordinate-system settings before running the workspace.
5. Open the result in a DWG-compatible CAD application and check drawing extents, units, layers, and representative features against the source.

If FME is unavailable, QGIS may be an option when its GDAL build exposes the SOSI reader. Export the features to DXF, then open that file in AutoCAD and use File → Save As to save as DWG. Check that the QGIS build can read the source SOSI version and review the DXF export’s layer and attribute handling. Use an online converter only if its current format list explicitly supports SOSI input and DWG output; do not upload restricted mapping data to an unapproved service.

Quality and compatibility

Conversion translates GIS features into CAD entities. SOSI topology, identifiers, attributes, and metadata may be omitted or represented differently; ordinary DWG entities do not retain GIS semantics automatically. Verify layer mapping, units, coordinate placement, and projection in the target application, and retain the original SOSI file when its attributes or spatial-reference details are needed later.