| map2lonlat {oce} | R Documentation |
Convert from x-y coordinates to longitude and latitude. This is normally called
internally within oce; see ‘Bugs’.
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’.
map2lonlat(x, y, init = NULL)
x |
vector containing the x component of points in the projected space, or
a list containing items named |
y |
vector containing the y coordinate of points in the projected space
(ignored if |
init |
vector containing the initial guesses for longitude and latitude, presently ignored. |
A list containing longitude and latitude, with NA
values indicating points that are off the globe as displayed.
oce uses rgdal::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.
Dan Kelley
lonlat2map() does the inverse operation.
A map must first have been created with mapPlot().
Other functions related to maps:
formatPosition(),
lonlat2map(),
lonlat2utm(),
mapArrows(),
mapAxis(),
mapContour(),
mapCoordinateSystem(),
mapDirectionField(),
mapGrid(),
mapImage(),
mapLines(),
mapLocator(),
mapLongitudeLatitudeXY(),
mapPlot(),
mapPoints(),
mapPolygon(),
mapScalebar(),
mapText(),
mapTissot(),
oceCRS(),
shiftLongitude(),
usrLonLat(),
utm2lonlat()
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)
}