oce (version 1.1-1)

map2lonlat: Convert X and Y to Longitude and Latitude

Description

Convert from x-y coordinates to longitude and latitude. This is normally called internally within oce; see ‘Bugs’.

Usage

map2lonlat(x, y, init = NULL)

Arguments

x

vector containing the x component of points in the projected space, or a list containing items named x and y, in which case the next argument is ignored.

y

vector containing the y coordinate of points in the projected space (ignored if x is a list, as described above).

init

vector containing the initial guesses for longitude and latitude, presently ignored.

Value

A list containing longitude and latitude, with NA values indicating points that are off the globe as displayed.

Bugs

oce uses project in the rgdal package to handle projections. Only those projections that have inverses are permitted within oce, and even those can sometimes yield errors, owing to limitations in rgdal. On i386/windows machines, the version of rgdal must be 1.3-9 or higher, to prevent an error with map2lonlat.

Details

A projection must already have been set up, by a call to mapPlot or lonlat2map. It should be noted that not all projections are handled well; see ‘Bugs’.

See Also

lonlat2map does the inverse operation.

A map must first have been created with mapPlot.

Other functions related to maps: lonlat2map, lonlat2utm, mapArrows, mapAxis, mapContour, mapDirectionField, mapGrid, mapImage, mapLines, mapLocator, mapLongitudeLatitudeXY, mapPlot, mapPoints, mapPolygon, mapScalebar, mapText, mapTissot, oceCRS, shiftLongitude, usrLonLat, utm2lonlat

Examples

# NOT RUN {
canProject <- .Platform$OS.type!="windows"&&requireNamespace("rgdal")
if (canProject) {
    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)
}

# }