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

[White.Denis at epamail.epa.gov]

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/
>
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