[Gdal-dev] OGR Error on State Plane transform

[Frank Warmerdam]

Garvan Keeley wrote:
> Thanks Frank,
> once the files were placed in the right place, the error went away and the
> transform was successful. 
> 
> I didn't realize there is an testing suite, where is that located?
> 
> Also, in the SetStatePlane function (SetStatePlane(int nZone, int bNAD83 =
> TRUE)) is the second argument indicating whether NAD27 or NAD83 are being
> used as input coordinates?
> If so, is SetWellKnownGeogCS() necessary in this instance?

Garvan,

Unlike SetUTM() or the various specific projection set methods, the
SetStatePlane() method sets the geographic coordinate system, not just
the projected coordinate system information.  This is because it is
essentially part of the definition of a state plane zone.  The bNAD83
flag indicates whether the NAD83 (TRUE) or NAD27 (FALSE) version of the
state plane zone should be generated.  Note, the actual projection
parameters and even the set of zones that exist vary somewhat between
the NAD27 and NAD83 versions.  The state plane zones also have "legally"
defined units, generally feet in NAD27 and meters in NAD83 which the
SetStatePlane() method sets.  The new override stuff is to addres the
common practice of using feet on NAD83 stateplane maps that are theoretically
supposed to all be in meters.

In short, you don't need SetWellKnownGeogCS() with SetStatePlane().

Best regards,

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