oce (version 0.9-14)

mapPlot: Plot a map

Description

Plot a map

Usage

mapPlot(longitude, latitude, longitudelim, latitudelim, grid=TRUE,
    bg, fill=NULL, type='l', axes=TRUE, drawBox=TRUE, showHemi=TRUE,
    polarCircle=0,
    projection="mollweide", parameters=NULL, orientation=NULL,
    debug=getOption("oceDebug"),
    ...)

Arguments

longitude

longitudes of points to be plotted, or an object with a slot named data that contains items named longitude and latitude (e.g. of class coastline; see

latitude

latitudes of points to be plotted

longitudelim

optional limit of longitudes to plot

latitudelim

optional limit of latitudes to plot

grid

either a number (or pair of numbers) indicating the spacing of longitude and latitude lines, in degrees, or a logical value indicating whether to draw a default grid with 15 degree spacing.

bg

background colour for plot (ignored at present).

fill

colour to be used to fill land regions, or NULL to avoid filling. For some map projections (particularly if the view includes the dateline), the filled region may not line up with coastlines, making it sensible to set

type

value to indicate type of plot, as with par("plot").

axes

logical value indicating whether to draw longitude and latitude values in the lower and left margin, respectively. This may not work well for some projections or scales.

drawBox

logical value indicating whether to draw a box around the plot. This is helpful for many projections at sub-global scale.

showHemi

logical value indicating whether to show the hemisphere in axis tick labels.

polarCircle

a number indicating the number of degrees of latitude extending from the poles, within which zones are not drawn.

projection

projection; see mapproject.

parameters

parameters for projection; see mapproject.

orientation

orientation for projection; see mapproject.

debug

a flag that turns on debugging. Set to 1 to get a moderate amount of debugging information, or to 2 to get more.

...

optional arguments passed to plotting functions.

Details

Creates a map using the indicated projection. The available projections can be found in the documentation for mapproject, which also provides information on the arguments named parameters and orientation. Further details on these and other projections are provided by Snyder (1987), an exhaustive treatment that includes many illustrations, an overview of the history of the topic, and some notes on the strengths and weaknesses of the various formulations. See especially pages 2 through 7, which define terms and provide recommendations.

References

Snyder, John P., 1987. Map Projections: A Working Manual. USGS Professional Paper: 1395 (available at pubs.usgs.gov/pp/1395/report.pdf).

Jenny, B., 2012. Adaptive composite map projections. IEEE Transactions on Visualization and Computer Graphics (Proceedings Scientific Visualization / Information Visualization 2012), 18-22, p 2575-2582.

XKCD guide to map projections (http://xkcd.com/977/).

See Also

Points may be added to a map with mapPoints, lines with mapLines, and text with mapText. Points on a map may be found with mapLocator. Great circle paths can be calculated with geodGc. Scale bars may be added with mapScalebar.

Examples

library(oce)
data(coastlineWorld)

## 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).
mapPlot(coastlineWorld, proj="mollweide")
mapPlot(coastlineWorld, proj="mollweide", orientation=c(90,-180,0))

## 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).  The
## examples given below illustrate use for low-latitude
## Pacific and high-latitude Atlantic/Arctic.
mapPlot(coastlineWorld, projection="orthographic",
        orientation=c(0,-180,0))
mapPlot(coastlineWorld, projection="orthographic",
        orientation=c(60,-40,0))

## 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.  Readers should compare the results
## with those with a polygonic projection, which is also popular.
mapPlot(coastlineWorld, longitudelim=c(-130,-55), latitudelim=c(35,60),
        proj="lambert", parameters=c(lat0=40,lat1=60),
        orientation=c(90,-100,0))

## The stereographic projection (Snyder 1987 page 120) is conformal,
## used below for an Arctic view with a Canadian focus.
mapPlot(coastlineWorld, longitudelim=c(-130,-50), latitudelim=c(70,110),
        proj="stereographic", orientation=c(90, -135, 0), fill='gray')