mollweide: Mollweide projection

In graphx: Graphics Routines for Scientific Research

Description

Performs a Mollweide projection (also known as Babinet projection, homalographic projection, homolographic projection, and elliptical projection) of longitude and latitude coordinates. The most important feature of the Mollweide projection is that it preserves surface areas, which makes it a commonly used projection in geography, astronomy and cosmology. The total surface area of the standard projection is equal to the surface area of the unit sphere (4pi); and the shape of the fully projected sphere is an ellipse (with axes lengths 2*sqrt(2) and sqrt(2)).

Usage

mollweide(lon, lat, lon0 = 0, radius = 1, deg = FALSE)

Arguments

lon	longitude or vector of longitudes in radians (unless deg=TRUE)
lat	latitude or vector of latitudes in radians (unless deg=TRUE), must lie between -pi/2 and +pi/2
lon0	latitude of null meridian, which will be projected on to x=0
radius	radius of spherical projection, such that the surface area of the projection equals 4piR^2
deg	logical flag; if set to TRUE, the input arguments lon, lat, lon0 are assumed to be in degrees (otherwise in radians)

Value

Returns a data frame of 2D Cartesian coordinates x and y.

Author(s)

Danail Obreschkow

Examples

lon = runif(1e4,0,2*pi)
lat = asin(runif(1e4,-1,1)) # = uniform sampling of the sphere
plot(mollweide(lon,lat),xlim=c(-3,3),ylim=c(-1.5,1.5),pch=16,cex=0.5)
plotrix::draw.ellipse(0,0,2*sqrt(2),sqrt(2),border='orange',lwd=2)

graphx documentation built on Feb. 3, 2022, 5:07 p.m.