Hi, I'm attempting a transformation between these two coordinate systems. I've tried by adding the GRS_1980 raster then selecting Transformations > Using, however the only option is <custom> New Geographic Transformation. I used this method then tried to clip the GRS_1980 raster to the OGSB_1936 however I dont think it has worked correctly as the GRS raster doesnt align and overlay properly with the OGSB raster. Anyone have any advice, some details on the datasets below.
Spatial coverage: Europe
Pixel size: 500m
Digital Elevation Model of area in southern England
You are using the Project Raster—Help | ArcGIS for Desktop tool, I presume. As the help topic suggests there is a transformation document (geographic_transformations.pdf) in you install directory ... C:\Program Files (x86)\ArcGIS\Desktop10.4\Documentation ... in my case 10.4 ... where you can find the transformation parameters if they haven't been implemented specifically
there may not be a transformation create, but you can at least compare the spheroids used to see if there are any matches...given that the latter one seems to be old
I would expect that the European data is on ETRS89 which uses GRS80. Can you redefine the (Define Projection or in "catalog") the geographic coordinate system for the raster to ETRS 1989? Then you should starting seeing OSGB_1936_To_ETRS_1989_1 as a possible transformation. It's file-based and will only affect data in the UK.
Edit: If you don't see that transformation, you might be on an earlier version that didn't have the grid file. Please post what software version you're using.