0

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.

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

enter image description here

Transforming Google Maps overlay to fit Ordnance Survey projection shows pretty much the opposite of what I am trying to do.

Improve this question
1
  • 1
    While this wont solve your aligment problem note that xyz google map use a projected crs (EPSG:3857 as shown on your pictures) rather than a geographic CRS as EPSG:4326 as you stated in your question….
    – J.R
    Jan 30 at 14:15

1 Answer 1

Reset to default
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.

Improve this answer
0

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

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