the volcano orientation

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 at 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 at 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 at gmail.com

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