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

[Roger Bivand]

Since this topic is of general interest, I've made an exception and 
allowed (this once!) a posting of more than 200K. In general, if graphics 
are big, please consider either an alternative device (png is often OK), 
or posting just a URL to the real file.

With apologies to list members on dial-up connections in the field,

Roger


On Thu, 5 Apr 2007 White.Denis at epamail.epa.gov wrote:

> 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/

-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no