[Proj] OSTN02 question: GRS80 instead of Airy.

[Paul Kelly]

Hello Roger

On Mon, 30 Oct 2006, Roger Oberholtzer wrote:

>
> Or not. If I change the +ellps=airy to +ellps=grs80, leaving all else
> the same, I see no difference at all.

Are you sure you removed the towgs84 and nadgrids parameters as well? 
There should definitely be a difference there. GRS80 and WGS84 are 
essentially the same thing at mapping-level scales - that is why there is 
no need for datum transformation. My earlier message was a little 
confusing, sorry.

Not sure which machine I developed that OSGB36 grid file on so can't check 
I'm afraid - it may have been on machine that I no longer have access to.

Paul