Calculate aspect ratio for plotting geographic maps; create nice degree axis labels

Calculate aspect ratio for plotting geographic maps; create nice degree axis labels

mapasp(data, xlim, ylim)
degreeLabelsEW(x)
degreeLabelsNS(x)

Arguments

data

object of class or extending Spatial

xlim

the xlim argument passed (or derived from bounding box)

ylim

the ylim argument passed (or derived from bounding box)

x

numeric; values at which tics and marks will be generated

Value

mapasp is used for the aspect argument in lattice plots and spplot;

let x = dy/dx, with dy and dx the y- and x-size of the map.

let s = 1/cos((My * pi)/180) with My the y coordinate of the middle of the map (the mean of ylim)

for latlong (longlat) data, mapasp returns s * x. for other data, mapasp returns "iso".

Note

the values for x are typically obtained from axTicks

See also

levelplot in package lattice