[gdal-dev] proj.4 +b parameter has different precision on i386 vs. amd64

[Frank Warmerdam]

On Tue, May 29, 2012 at 7:38 AM, Etienne Tourigny
<etourigny.dev at gmail.com> wrote:
> Hi list,
>
> It seems that the +b parameter of Proj.4 strings generated by gdal can
> have different precisions, dependent on the architecture (i386 vs.
> ams64) for various linux flavors and gdal versions (1.6 - 1.9).
>
> The CRS from EPSG:4131 can have slightly different values: (
> +b=6356075.413140239 vs. +b=6356075.41314024 )
>
> i386:
> +proj=utm +zone=48 +a=6377276.345 +b=6356075.413140239
> +towgs84=198,881,317,0,0,0,0 +units=m +no_defs
>
> amd64:
> +proj=utm +zone=48 +a=6377276.345 +b=6356075.41314024
> +towgs84=198,881,317,0,0,0,0 +units=m +no_defs
>
>
> ==> Can this happen with other values?

Etienne,

I imagine it can, though this value is particularly
sensitive to it since it is computed.

> ==> Is it an artifact of the calculation of the semi-minor axis from
> semi-major and inv-flattening in ogr_srs_proj4.cpp ?
> ==> Is this a bug?

In my opinion it is not a bug.

Best regards,
-- 
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