[mapserver-users] request help with projection

[Frank Warmerdam]

David Armstrong wrote:

> 
> Could someone on the list confirm if i have this correct :-
> 
> I need to use projection using 2 layers , one being my map and the other
> being my gps , the gps unit is fixed in WGS84 and the datum etc cannot be
> changed , and i am trying to overlay my gps layer on the map.
> 
> the map i have is :-
> NAD_1927_Stateplane_Texas_South_Central_Fips_4204
> 
> Looking this up i belive the map layer  projection should be
> 
> PROJECTION
> proj=lcc
> datum=NAD27
> END
> 
> and the gps layer  should be
> 
> WGS84 Decimal Degrees (EPSG 4326)
> PROJECTION
>    proj=latlong
>    ellps=wgs84
> END
> 
> Should i just be able to set the output map to the same as the map layer for
> correct use !


David,

I think you need to use:


 > PROJECTION
 >    proj=latlong
 >    datum=WGS84
 > END

Saying the ellipse is WGS84 isn't quite the same as saying the datum is, and so
PROJ won't try to do the datum conversion.  At least I imagine that is your
problem.

Best regards,

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