[R] the volcano orientation

[Richard O'Keefe]

Like other countries, New Zealand revises its maps and its coordinate
system from time to time.  The one in use at the time that image was
digitised is probably the one described here:
https://www.linz.govt.nz/data/geodetic-system/datums-projections-heights/projections/new-zealand-map-grid-nzmg

On Tue, 12 May 2020 at 04:58, John via R-help <r-help using r-project.org> wrote:
>
> Out of curiosity, and considering the bewildering array of projections
> and grids in use for various mapping purposes, you seem to be saying in your
> example 2 that the grid coordinates number south to north and east to
> west.  Given scale of the coordinate numbers, would that be a national
> grid system employed in New Zealnd?
>
> J. W. Dougherty
>
> On Mon, 11 May 2020 13:56:49 +1200
> "Richard O'Keefe" <raoknz using gmail.com> wrote:
>
> > Hey, I know that volcano!  It's walking distance from the Intermediate
> > school I attended.
> > To you it's a plot; to me it's a place.
> > So I offer you four scenarios.
> >
> > 1. You think of it as a place you know and have been.
> >     In that case the "right" orientation is the one that best matches
> > what you are used to seeing.
> >     For me, that would put the peak on the right of the plot.
> >
> > 2. You think of it as a patch in a map.
> >     In that case the "right:" orientation is the one that matches the
> > map. That would put the peak at the bottom of the plot.
> >
> > 3. You think of it as a product of geological processes, and are
> > perhaps interested in
> >     whether there is any connection between the orientation of the
> > volcano and the
> >     direction the Auckland hot-spot (currently at White Island) was
> > moving. In that case you'd choose south-west -> north-east as the
> > primary axis. (I think.  Not really sure.)
> >
> > 4. You think of it as a picture, an illustration in a textbook.  It
> > might need to be cropped
> >     vertically so you can fit another illustration on the same page.
> > For that and
> >     perceptual reasons you want the major linear axis of the image to
> > be  horizontal.
> >     In that case, what we have now is a perfectly reasonable choice.
> >
> > "Quality is fitness for use."
> >
> > On Sun, 10 May 2020 at 12:44, Michael Sumner <mdsumner using gmail.com>
> > wrote:
> > >
> > > Does anyone know why 'volcano' is oriented as it is?
> > >
> > > image(volcano)  ## filled.contour is the same
> > >
> > > I know it's all arbitrary, but north-up is a pretty solid
> > > convention. Is there any reason why the classic 'image()' example
> > > data set would not default to this orientation?
> > >
> > > A Google map of the site (in Web Mercator):
> > >
> > > https://www.google.com/maps/place/Maungawhau+%2F+Mount+Eden/@-36.8763271,174.7619561,856m/data=!3m1!1e3!4m8!1m2!2m1!1smaungawhau!3m4!1s0x6d0d47db8d7bd1ff:0x8bcffe2a5c7360d2!8m2!3d-36.8666667!4d174.7666667
> > >
> > >
> > > For image(), the north-up orientation is
> > > 't(volcano[,ncol(volcano):1])'.
> > >
> > > If you are interested in a roughly georeferenced version I have
> > > code here:
> > >
> > > https://gist.github.com/mdsumner/20fe3ffa04421bf8e0517c19085e5fd8
> > >
> > > (Also see fortunes::fortune("conventions") )
> > >
> > > Best, Mike
> > >
> > >
> > > --
> > > Michael Sumner
> > > Software and Database Engineer
> > > Australian Antarctic Division
> > > Hobart, Australia
> > > e-mail: mdsumner using gmail.com
> > >
> > >         [[alternative HTML version deleted]]
> > >
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