Site Context DXF guide
Georeferenced context plans of any site in Great Britain, from OpenStreetMap, ready to open in AutoCAD or link into Revit in true British National Grid (EPSG:27700).
Steps
- Set the centre of the site: type the easting and northing (e.g.
538624, 183551), paste latitude/longitude from Google Maps (e.g.51.533853, -0.002787), click the map, or drag the tile. - Set the tile size: width (east-west) and height (north-south), 0.25 to 5 km each.
- Choose the units: millimetres or metres. Use the same units when you import.
- Choose the outputs (see below) and press Generate DXF. Wait for the spinner to stop.
- Download the files one by one, or all at once with Download all (ZIP).
To make another plan, change the point or the size and press Generate DXF again. The page address always holds the current site and size: copy it, or use Copy link, to share exactly the same tile.
Which file to use
Files are named after the OS grid reference of the centre, e.g. TQ386835_OSM_Clean_mm.dxf.
| File | What it is | Use it for |
|---|---|---|
…_Raw | Everything mapped in OpenStreetMap, each type on its own layer (also fences, car parks, boundaries, power lines, bus and cycle routes) | Picking out something the clean plans leave out |
…_Clean | Curated plan: buildings, roads, kerbs, pavements, green areas, water edges, railways, stations, labels, scale bar and north arrow | A base to draw over, or to link into Revit |
…_Clean-Shaded | The same plan with buildings and water filled | Presentations and sheets |
…_README.txt | Centre, tile, units, data date and attribution | Keeping a record |
| JPG button | Image of the whole sheet, 4000 px wide | Reports, emails, slides. It has no scale or coordinates |
All plans carry a British National Grid with coordinates outside the frame, and a lineweight per layer, so they print without a CTB.
Linking into Revit
- Insert › Link CAD and choose the DXF.
- Set Import units to the units you chose (millimetres or metres).
- Set Positioning to Auto – Center to Center and link it.
- Manage › Coordinates › Acquire Coordinates, and click the linked DXF.
The project now uses British National Grid as its shared coordinates. If you align the internal origin to a point, use an intersection of the plan's grid.
If something goes wrong
- It keeps waiting, or says the servers are busy. The data comes live from public OpenStreetMap servers (Overpass), which are sometimes overloaded. The app tries five servers for up to 6 minutes and shows how long it has waited. Try again a few minutes later, or with a smaller tile.
- Large tiles are slow. Tiles over 3 km, especially in central London, can take a few minutes and give files of tens of MB.
- The map does not appear. Check your internet connection. On a company network, IT may need to allow
unpkg.com,tile.openstreetmap.org,server.arcgisonline.com(satellite) and the Overpass servers. - Something is missing from the plan. The plans only show what volunteers have mapped in OpenStreetMap. Detail varies by area; kerbs, for example, are only mapped in parts of London.
Good to know
Accuracy: a few metres. This is context, not a measured survey: do not dimension from it.
Attribution: plans must credit "© OpenStreetMap contributors" (ODbL). The note is already written under the frame; keep it.
Grid north: the plans and the map are aligned to grid north, which differs from true north by 1–2° across Great Britain.