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”.
Usage
map2lonlat(x, y, init = NULL, debug = getOption("oceDebug"))Arguments
- x
vector containing the x component of points in the projected space, or a list containing items named
xandy, in which case the next argument is ignored.- y
vector containing the y coordinate of points in the projected space (ignored if
xis a list, as described above).- init
vector containing the initial guesses for longitude and latitude, presently ignored.
- debug
an integer specifying whether debugging information is to be printed during the processing. This is a general parameter that is used by many
ocefunctions. Generally, settingdebug=0turns off the printing, while higher values suggest that more information be printed. If one function calls another, it usually reduces the value ofdebugfirst, so that a user can often obtain deeper debugging by specifying higherdebugvalues.
Value
A list containing longitude and latitude, with NA
values indicating points that are off the globe as displayed.
Bugs
oce uses the sf::sf_project() function to handle projections.
Only those projections that
have inverses are permitted within oce, and of that subset, some are omitted
because the oce developers have experienced problems with them.
See also
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(),
oceProject(),
shiftLongitude(),
usrLonLat(),
utm2lonlat()
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)
#> $longitude
#> [1] -64.49657
#>
#> $latitude
#> [1] 45.33462
#>