Inserting a Spatial reference
The guidance you are looking for will vary because it depends on the map you start with--there are many, too many, variables.
Please provide more info. Can you share your Ordnance Survey scale base map for analysis? If it has enough info, hopefully it does, then a procedure can be provided. Without that survey no meaning instructions can possibly be offered.
Also AutoCAD are you running? Version and release year?
Feel free to use private message if you wish.
Chicagolooper
Thank you for sharing.
National Trust, Arrington, correct?
You don't need to move, scale, or rotate your drawing. You can save your original drawing to dxf. Also, copy the info that's shown below (blue text) then paste it into Word, Notepad, or directly into the body of an email—it should accompany your dxf when you send it. If you need more geospatial assistance, just ask.
As noted earlier, your drawing is already spatially accurate. You don’t ‘technically’ need a georef'd dxf file b/c your coordinates are already consistent w/OSGB 1936 grid but I’ve attached a georef’d dxf anyway.
The georeference is
OSGB 1936.NationalGrid (meters)
EPSG 27700
To get a non-gepref’dxf (yes, it’ll work even if your saved dxf is not geospatial):
Use SAVEAS=>then save with .dxf extension (refer to image below).
Unfortunately AutoCAD cannot Import nor Export json. So for your specific need the dxf format is the most AutoCAD can do.
Here's a small portion of your drawing. Bing imagery is in the background.
Chicagolooper
@eddlewington wrote:...Can I also ask how I check whether a Geo reference already exists in a .dwg...
Yes, method from @pendean will work because it will display the CS that's currently assigned.
It will not, however, verify whether the CS assigned is the RIGHT one.
Chicagolooper
<<...How do I bring up the Bing imagery within Autocad without importing it?...>>
Regarding you uploaded drawing named Westonbirt Topographical and Utility Survey - Updated APR 2025.dwg You can do this:
1. On your layout tab, activate the viewport.
2. With the viewport activated, go to Online Map Panel=>Map Aerial=>Capture Viewport
3. You may now change from Map Aerial to Map OFF because you captured the viewport's image--even though it's turned Off, that captured image is now sitting in modelspace.
<<Technically speaking the Captured imaged is not an XREF. Your captured image will not appear in the External References palette. If you STRETCH an edge or corner of the image to make it bigger than your original captured area, you'll notice the stretching operation will cover more area and still be geospatially accurate. This behavior is not XREF behavior, it's more like you're streaming pixels over the internet because the coverage area remain live.>>
4. OPTIONAL: In modelspace=>select the captured image=>go to Properties Palette and increase value of Brightness. (Brightness can also be controlled on the Ribbon.) I recommend brightness=80. Brightness values from 60 to 80 will frequently give best results, although some images may vary.
Do NOT recommend changing contrast or fade--leave them at their default, 50 and 0 respectively. Also, print a hardcopy before deciding on your brightness value. A hardcopy is an immense help when deciding the brightness. Changing brightness is optional. And don't forget, your linework should bear the load in your dwg, not the image.
Chicagolooper
