[Proj] MapInfo/Oracle Cylindrical Miller Parameters

[Frank Warmerdam]

On 1/12/06, Patrick Mézard <pmezard at gmail.com> wrote:
> Hello,
>  In search of a good-looking world projection I came across Miller
> Cylindrical one. Fortunately, both MapInfo and Oracle Spatial know about it,
> and even better agree on transformations from WGS84 to Miller for several
> points. This is important because it is always easier to debug something
> when the input or output can be reproduced on other tools. Now I would like
> to use it in proj.4 but as usual I am stuck trying to figure out *the
> parameter string*.
>
>  I am taking the Oracle WKTEXT description as reference:
>  """
>  PROJCS["Miller Cylindrical", GEOGCS [ "NAD 27 (Continental US)", DATUM
> ["NAD 27 (Continental US)", SPHEROID ["Clarke 1866", 6378206.400000,
> 294.978698]], PRIMEM  [ "Greenwich", 0.000000 ], UNIT ["Decimal Degree",
> 0.01745329251994330]], PROJECTION ["Miller Cylindrical"], UNIT ["Meter",
> 1.000000000000]]
>  """
>
>  It converts (2.35, 48.85) into (261360.667, 5916639.52).

Patrick,

As John notes, it is a bit artificial to be using a NAD27 based
miller projection for world mapping.

If I use "proj -V" to get more details of how PROJ.4 treats
your projection definition we see that it operates only on spheres
for Miller, and derives a sphere of radius 6378206.400.  I suspect
that Oracle is either actually evaluating the projection on the
ellipsoid, or falling back to a different sphere definition.

It may be difficult to get compatible results if some systems
are evaluating miller on the ellipsoids while PROJ.4 only does it
on the sphere.

Best regards,
--
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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