geographical accuracy

Graham Seaman graham at
Wed Feb 21 15:33:21 GMT 2007

Andy Armstrong wrote:
> On 21 Feb 2007, at 14:43, Graham Seaman wrote:
>> This improves the output but by a tiny amount (typically a change in 
>> the 4th decimal place of the lat/long) which is smaller than the 
>> error.  Do you know what the correct scalefactor  for wgs84 is? I've 
>> tried googling with no results so far...
> I'm not sure what that's doing so I don't know :)
It seems to be known cryptically as 'Fo' in equations...
The source comments just say 'scale factor on the meridian'

> As an alternative you could try converting the OSGB36 lat/lon to WGS84 
> using
> That'd at least allow you to confirm that that's the problem.
Will do.
> Another check: take your easting, northing and paste them into 
> to see if they have the same error there.
Brilliant, I hadn't even realised it accepted them - and my 
northings/eastings are perfect, so now I know for sure it's a conversion 
problem :-) Thank you very much indeed...


> --Andy Armstrong,

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