[OSGeo-UK] OSGB36 WGS84 conversion problem

[Stuart Eve]

Hey there

I came across this problem before and had to make some adjustments to  
my epsg file. Try replacing the current <27700> line in your epsg file  
with this one:

# OSGB 1936 / British National Grid
<27700> +proj=tmerc +lat_0=49 +lon_0=-2 +k=0.999601 +x_0=400000  
+y_0=-100000 +ellps=airy  
+towgs84=446.448,-125.157,542.060,0.1502,0.2470,0.8421,-20.4894  
+units=m +no_defs no_defs <>

Hopefully that will sort your problem

Best

Stuart

Stuart Eve
L - P : Archaeology
stuarteve at gmail.com
On 13 Jul 2009, at 15:33, John A Stevenson wrote:

> Hi,
>
> I have been using GRASS GIS, which uses Proj4 to convert between  
> projections.  I have data in OSGB36 projection (a Nextmap DEM and a  
> scanned in OS map), and I am trying to merge it with GPS data (from  
> WGS84).  When I do the conversion (using EPSG:27700) I find that the  
> GPS data plot about 100 m east of where they should do.
>
> Has anyone else had this trouble converting between OSGB36 and WGS84  
> coordinate systems?  What is the solution?  Are there any other  
> conversion parameters available?
>
> Cheers
>
> John
>
> -- 
>
>
> Dr John Stevenson
> Postdoctoral Research Associate
> School of Earth, Atmospheric and Environmental Sciences
> Williamson Building (Room 2.42)
> University of Manchester
> Manchester M13 9PL, UK
> tel. +44(0)161 306 6585; fax. +44(0)161 306 9361;
> john.stevenson at manchester.ac.uk
> _______________________________________________
> UK mailing list
> UK at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/uk

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