Overview. The contents here are derived from the help page on mapPlot(). Things are coming along, but there are some known problems:

  1. Axis labels are scrambled in the stereographic plot. This is a known problem, solved in another Oce branch.
  2. Filling is not working on the stereographic plot.
  3. The proj4/orthographic case is very slow (problem and patch reported to the proj4 author today).

Mollweide is an equal-area projection that works well for whole-globe views, below shown in default and Pacific-focus views. See Snyder (1987 page 54).

library(oce)
data(coastlineWorld)
par(mfrow=c(1,2), mar=c(1, 1, 1, 1))
mapPlot(coastlineWorld, proj="mollweide", orientation=c(90,-180,0))
mtext("Mollweide/mapproj", adj=1)
mapPlot(coastlineWorld, proj="+proj=moll +lon_0=-180")
mtext("Mollweide/proj4", adj=1)

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Orthographic projections resemble a globe, making them attractive for non-technical use, but they are neither conformal nor equal-area, so they are somewhat limited for serious use on large scales. See Snyder (1987 section 20).

par(mfrow=c(1,2), mar=c(1, 1, 1, 1))
mapPlot(coastlineWorld, projection="orthographic", orientation=c(0,-180,0))
mtext("Orthographic/mapproj", adj=1)
mapPlot(coastlineWorld, projection="+proj=ortho +lon_0=-180")
mtext("Orthographic/proj4", adj=1)

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The Lambert conformal conic projection is an equal-area projection recommended by Snyder for regions of large east-west extent away from the equator, here illustrated for the USA and Canada..

par(mfrow=c(1,2), mar=c(3, 3, 1, 1))
mapPlot(coastlineWorld, longitudelim=c(-130,-55), latitudelim=c(35,60),
        proj="lambert", parameters=c(lat0=40,lat_1=60), orientation=c(90, -100, 0))
mtext("Lambert/mapproj", adj=1)
mapPlot(coastlineWorld, longitudelim=c(-130,-55), latitudelim=c(35,60),
        projection="+proj=lcc +lon_0=-100 +lat_0=40 +lat_1=60")
mtext("Lambert/proj4", adj=1)

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The stereographic projection (Snyder 1987 page 120) is conformal, used below for an Arctic view with a Canadian focus. Note the trick of going past the pole: the second latitudelim value is 180 minus the first, and the second longitudelim is 180 plus the first; this uses image points “over” the pole.

par(mfrow=c(1,2), mar=c(3, 3, 1, 1))
mapPlot(coastlineWorld, longitudelim=c(-130,50), latitudelim=c(70,110),
        proj="stereographic", orientation=c(90, -135, 0), fill='gray') 
mtext("Stereographic/mapproj", adj=1)
mapPlot(coastlineWorld, longitudelim=c(-130,50), latitudelim=c(70,110),
        proj="+proj=stere +lat_0=90 +lon_0=-135") #, fill='gray')
mtext("Stereographic/proj4", adj=1)

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