[R-sig-Geo] Help with latlong to UTM conversion when UTM zones are different

[Barry Rowlingson]

On 27 Mar 2015 23:50, "Robert J. Hijmans" <r.hijmans at gmail.com> wrote:
>
> Are these really reasonable reasons? I do not think so, given that the
> question had nothing to do with map navigation and the person asking
> appears to live in the UK.

??? How did you figure that out? He gave some phone numbers that had
Botswana country codes and a southern hemisphere utm zone code! Elementary
my dear Robert!

But yes, as I said, if there's a local standard use it. To find the local
standard, buy a paper map and read the projection info! I would never use
UTM in the uk when epsg:27700 is our standard.

> Moreover, other projections have, or can
> have, their units in meters as well (or feet or miles or whatever you
> might fancy). UTM indeed appears to be an unfortunate default that
> deserves some pushback.

I see utm as a last resort rather than a default. However finding a better
coordinate system in the maze of epsg codes can lead to people using the
wrong thing, and unless you span several zones, utm is never that wrong...

> Robert
>
> On Fri, Mar 27, 2015 at 2:28 PM, Michael Sumner <mdsumner at gmail.com>
wrote:
> > They are reasonable reasons, but traversing zones is a pain, you should
see
> > if using one or the other is sufficient. I would check carefully the
> > distances you get against ellipsoidal calculations.
> >
> > Cheers, Mike
> >
> > On Sat, 28 Mar 2015 07:30 Andrew Duff <andrewaduff at gmail.com> wrote:
> >
> >> A number of field folks prefer UTM because
> >>
> >> -it matches legacy paper USGS quad map series traditionally used for
field
> >> navigation
> >> -units are in meters and can be used to gauge field distances from a
> >> coordinate readout
> >>
> >>
> >>
> >> > On Mar 27, 2015, at 10:48 AM, Michael Sumner <mdsumner at gmail.com>
wrote:
> >> >
> >> > There is no good natural reason to use UTM, it mistifies me why our
> >> > community tolerates this bizarre default. I always use a local
equal-area
> >> > projection unless some other compromise dictates a different choice.
> >> > Cheers, Mike
> >> >
> >> > On Fri, 27 Mar 2015 21:28 Barry Rowlingson <
b.rowlingson at lancaster.ac.uk
> >> >
> >> > wrote:
> >> >
> >> >> If you have lat-long data that crosses two UTM zones then its
> >> >> generally okay to just pick *one* and transform all the points to
> >> >> that. Use the one that has the most points in. Basically use the UTM
> >> >> zones as guidelines to pick one UTM zone coordinate system. Unless
> >> >> your data spans several zones and you want quite high accuracy of
> >> >> distance measurements. Some points bleeding over into an adjacent
zone
> >> >> are no problem.
> >> >>
> >> >> All projections are approximations to the earth's spheroid, so
points
> >> >> that are within a single UTM zone have some distortion in their
> >> >> distance or angle relationships. Transforming points that are within
> >> >> an adjacent UTM zone is just an extension of that distortion. You
can
> >> >> compute the precise distance error if you want for the furthest
points
> >> >> by comparing with the geodesic distance.
> >> >>
> >> >> Alternatively you might find there is a coordinate system that spans
> >> >> your dataset nicely - often when a country or an island or a region
> >> >> crosses UTM zones there is an official coordinate system defined
that
> >> >> is used by the authorities there.
> >> >>
> >> >> Also alternatively, there's nothing to stop you defining a
transverse
> >> >> mercator system based on the centre of your data.
> >> >>
> >> >> Barry
> >> >>
> >> >>
> >> >>
> >> >> On Fri, Mar 27, 2015 at 7:44 AM, moses selebatso <
> >> selebatsom at yahoo.co.uk>
> >> >> wrote:
> >> >>> Hello
> >> >>> I have animal movement data that I have converted from Lat/Long to
UTM,
> >> >> unfortunately the data falls in two UTM zones (34S and 35S). For
some
> >> >> reason R cannot display both of them in the same window (the 35S
data is
> >> >> way off the expected location).
> >> >>> The question is how do I convert the data such that R can correctly
> >> read
> >> >> it?
> >> >>> Moses SELEBATSO
> >> >>>
> >> >>> (+267) 318 5219 (H) (+267) 716 393 70 (C)
> >> >>>  (+267) 738 393 70 (C
> >> >>>        [[alternative HTML version deleted]]
> >> >>>
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