0

I would like to ask you how can I fix the overlaid of the. Geotiff Ordnance Survey maps with the XYZ Google Maps. I know, that Google uses the EPSG:4326 WGS84 ordinance system, whereas Ordnance Survey uses OSGB British National Grid EPSG 27700. I know also where to change the CRS, but if I change the CRS in my project reference it still comes with the enter image description herewrong overlay. Unfortunately, the difference is too big, over 2m. How can I make it matching to Google Maps overlay? If I can't is there a way to trim down these differences?

I have an option to transform my coordinates, but I don't know which one should be correct.

enter image description here

The query below shows pretty much the opposite side of my exercise

Transforming Google Maps overlay to fit Ordnance Survey projection

Thanks

8
3

You wouldn't expect them to line up.

OS is the correct location, Google is an approximately correct location, based on an automated georeferencing of satellite imagery.

You might get a slightly better fit by using a grid file transformation. But the transformation you are using now would only account for up to 1 meter of offset.

See:

https://www.ordnancesurvey.co.uk/business-government/tools-support/os-net/format

How to use gridfiles (*.gsb) in QGIS 3.10.0-2

But the only way you will get them to line up is by exporting the Google map is an image and reprojecting it yourself to line up.

Satellite imagery will always have some sort of offset compared to a ground truth dataset.

2
  • Great! It looks slightly better. Regrettable it looks like the file is valid on the OS maps provided directly by the Ordnance Survey. How about the maps from the other providers. Should I copy another .gsb file or set up the existing one? – MKR Jun 24 '20 at 16:23
  • Same gsb. It is just defines the transformation between BNG and WGS84. – HeikkiVesanto Jun 24 '20 at 16:41

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.