Your question seems to need an answer to, "How do you find a convex hull on a sphere?" Google has many references.

Clint Bowman                    INTERNET:       cl...@ecy.wa.gov
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On Fri, 15 Aug 2014, Bob O'Hara wrote:

I've been struggling for half a day on what should be a simple problem...

I have a data frame of lat/long coordinates that describe a region, and I
want to draw a polygon around them so I can use that as a boundary (to be
thrown at INLA, but those details aren't important). The coordinates are
almost on a regular grid: there is some variation in latitude (because
we're on a globe).

If the coordinates were on a regular grid, I could use as.owin() to create
a mask, and go on from there (I have code that will work). But as.owin()
doesn't like unevenly spaced points.

Can anyone suggest a way to sort this out? Preferable without having to
mess around transforming the coordinates.

Bob

--
Bob O'Hara

Biodiversity and Climate Research Centre
Senckenberganlage 25
D-60325 Frankfurt am Main,
Germany

Tel: +49 69 798 40226
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Journal of Negative Results - EEB: www.jnr-eeb.org

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