The calculation is done by finding a minimum value of a cost
function that is the vector difference between (x,y)
and the corresponding values returned by geodXy.
See “Caution”.
geodXyInverse(x, y, longitudeRef, latitudeRef,
debug = getOption("oceDebug"))value of x in metres, as given by geodXy
value of y in metres, as given by geodXy
reference longitude, as supplied to geodXy
reference latitude, as supplied to geodXy
an integer specifying whether debugging information is
to be printed during the processing. This is a general parameter that
is used by many oce functions. Generally, setting debug=0
turns off the printing, while higher values suggest that more information
be printed. If one function calls another, it usually reduces the value of
debug first, so that a user can often obtain deeper debugging
by specifying higher debug values.
a data frame containing longitude and latitude
This scheme is without known precedent in the literature, and users should read the documentation carefully before deciding to use it.
The minimum is calculated in C for speed, using the nmmin function
that is the underpinning for the Nelder-Meade version of the R function
optim. If you find odd results, try setting debug=1
and rerunning, to see whether this optimizer is having difficulty
finding a minimum of the mismatch function.
Other functions relating to geodesy: geodDist,
geodGc, geodXy