oce (version 0.9-17)

lonlat2map: Convert from longitude and latitude to x-y coordinates

Description

Convert from longitude and latitude to x-y coordinates

Usage

lonlat2map(longitude, latitude,
          projection="", parameters=NULL, orientation=NULL)

Arguments

longitude

a vector containing decimal longitudes, or a list containing items named longitude and latitude, in which case the indicated values are used, and next argument is ignored.

latitude

a vector containing decimal latitude (ignored if longitude is a list, as described above).

projection

optional indication of projection. This is normally a string in the format used by the proj4 package, i.e. starting with +proj=. (See the Deprecation notice for

parameters,orientation

See Deprecation notice for mapPlot.

Value

• A list containing x and y.

Deprecation notice

At the moment of writing, it is still also possible to specify projections using projection, parameters and orientation in the terminology employed by the mapproj package. In that case, the calculations are done using that package (if it is installed). Unfortunately, this method can yield poor results, because inverse-projection is not handled by mapproj. For this reason, this capability is likely to be removed in a future version of oce. It is only provided in the present version to give users time to alter their code. It will be removed sometime in the year 2015.

Details

If a projection is already being used (e.g. as set by mapPlot) then only longitude and latitude should be given, and the other arguments will be inferred by lonlat2map. This is important because otherwise, if a new projection is called for, it will ruin any additions to the existing plot.

See Also

mapLongitudeLatitudeXY is a safer alternative, if a map has already been drawn with mapPlot, because that function cannot alter an existing projection.

Examples

library(oce)
## Cape Split, in the Minas Basin of the Bay of Fundy
cs <- list(longitude=-64.49657,latitude=45.33462)
xy <- lonlat2map(cs, projection="+proj=merc")
map2lonlat(xy)