[Proj] Meaning of 7-parameter transformation rotations

Martin Vermeer martin.vermeer at hut.fi
Wed Nov 30 15:52:55 EST 2005

On Wed, Nov 30, 2005 at 12:05:06PM -0500, Frank Warmerdam wrote:
> On 11/30/05, Martin Vermeer <martin.vermeer at hut.fi> wrote:
> > Yes, I know. Just wanted to point out that the above quoted text is
> > uninformative. Yes, the exact matrix contains sines and cosines, but of
> > the angles Rx, Ry, Rz that are in seconds of arc (and thus, in any
> > computation, must be converted to radians first).
> >
> > The text following "not in physical units" just expresses the author's
> > lack of information, and contains a wrong guess. I propose to replace it
> > by correct information.
> Martin,
> Thanks, I have updated the paragraph to read:
> "The seven parameter case uses <i>delta_x</i>, <i>delta_y</i>, <i>delta_z</i>,
> <i>Rx - rotation X</i>, <i>Ry - rotation Y</i>, <i>Rz - rotation Z</i>,
> <i>M_BF - Scaling</i>.  The three translation parameters are in meters as
> in the three parameter case.  The rotational parameters are in seconds of
> arc.  The scaling is apparently the scale change in parts per million."
> Does this look OK?  The previous text was intended to highlight my
> lack of information.
> Best regards,



- Martin

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