[R-sig-Geo] Good projection for N/S America?

[White.Denis at epamail.epa.gov]

Yes, for many uses that is my choice also.  For the conterminous US for
example, the Lambert azimuthal has lower mean distortion than the
commonly used standard projection, the Albers conical equal area,
although Albers was chosen by USGS as a standard because of lower
extreme distortion than many other possible projections.

For our hemispherical application, because we were gridding the data, we
wanted parallels of latitude to be parallel in the projected coordinate
space, which we wouldn't get with the Lambert azimuthal.

(See attached file: whemi.projs.pdf)

Tim Keitt <tkeitt at gmail.com> wrote on 2007-04-05 10:56:09:

> Thanks. My application is not that demanding. Really, I just want it
> to look reasonable. My plan is to lay out the postings in the
> projected coordinates and then back transform into geographic
> coordinates for analysis. I tried lots of projections and found
> Lamberts Azimuthal Equal Area to be quite good. I like the look of the
> Azimuthal Equidistant better, but figured equal area was a good
> choice.
>
> THK
>
> On 4/4/07, White.Denis at epamail.epa.gov <White.Denis at epamail.epa.gov>
wrote:
> > Tim,
> >
> > It depends on which kind of distortion is of most concern.  For many
> > types of extensive data, especially counts, for example, the equal
area
> > property is desirable.  We used the Lambert cylindrical equal area
> > projection with standard parallels of +/- 30 degrees for some
western
> > hemispherical work, see reference below.  (The center longitude
could be
> > -80 west, but that is less important than the choice of parallels.)
> >
> > Before falling back on the Lambert as an easy to use projection, I
tried
> > to get several ESRI products to implement an interrupted projection
> > using the sinusoidal projection, in part for reasons given in the
second
> > reference.  I used a separate center longitude for north and south
of
> > the equator and the appearance is certainly more satisfactory than
the
> > Lambert in my opinion.  I'll attach a PDF of an illustration of this
> > approach generated in R that I hope you will get but not the rest of
the
> > list unfortunately.  I can send PDFs of the references also if
needed.
> >
> > Denis
> >
> > Lawler JJ, White D, Neilson RP, Blaustein AR.  2006.  Predicting
> > climate-induced range shifts: model differences and model
reliability.
> > Global Change Biology 12:1568-1584.
> >
> > White D.  2006.  Display of pixel loss and replication in
reprojecting
> > raster data from the sinusoidal projection.  Geocarto International
> > 21(2):19-22.
> >
> > (See attached file: whemi.sinus.pdf)
> >
> > r-sig-geo-bounces at stat.math.ethz.ch wrote on 2007-04-04 12:17:39:
> >
> > > Anyone know of a particularly good map projection for showing all
of
> > > North and South America without too much distortion?
> > >
> > > THK
> > >
> > > --
> > > Timothy H. Keitt, University of Texas at Austin
> > > Contact info and schedule at http://www.keittlab.org/tkeitt/
> > > Reprints at http://www.keittlab.org/tkeitt/papers/
> > > ODF attachment? See http://www.openoffice.org/
> > >
> > > _______________________________________________
> > > R-sig-Geo mailing list
> > > R-sig-Geo at stat.math.ethz.ch
> > > https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> >
>
>
> --
> Timothy H. Keitt, University of Texas at Austin
> Contact info and schedule at http://www.keittlab.org/tkeitt/
> Reprints at http://www.keittlab.org/tkeitt/papers/
> ODF attachment? See http://www.openoffice.org/
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