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\name{RMtrafo}
\alias{RMtrafo}
\alias{RFearth2cartesian}
\alias{RFearth2dist}
\title{Transformation of coordinate systems}
\description{
The functions transform a coordinate system into another coordinate system.
Currently, essentially only from the earth system to cartesian.
\command{RMtrafo} is the internal basic function that also allows
to reduce vectors to their norm.
}
\usage{
% to do: auch fuer die 'plane' transformationen
RMtrafo(phi, new)
RFearth2cartesian(coord, units=NULL, system="cartesian", grid=FALSE)
RFearth2dist(coord, units=NULL, system="cartesian", grid=FALSE, ...)
}
\arguments{
\item{new}{integer or character. One of the values
\code{\link[=constants]{RC_ISOTROPIC}},
\code{\link[=constants]{RC_SPACEISOTROPIC}},
% ZEROSPACEISO,
% VECTORISOTROPIC,
% SYMMETRIC,
\code{\link[=constants]{RC_CARTESIAN_COORD}},
\code{\link[=constants]{RC_GNOMONIC_PROJ}},
\code{\link[=constants]{RC_ORTHOGRAPHIC_PROJ}}
% EARTH_COORD,
% SPHERICAL_COORD,
% CYLINDER_COORD
or the corresponding \code{\link[=constants]{RC_ISONAMES}}.
Note that \command{RMtrafo} only allows for integer values.
Default: \code{RC_CARTESIAN_COORD}.
}
\item{phi}{optional submodel}
\item{coord}{matrix or vector of earth coordinates}
\item{units}{"km" or "miles"; if not given and
\code{RFoptions()$general$units != ""}, the latter is used.
Otherwise \code{"km"}.
}
\item{system}{integer or character. The coordinate system, e.g.
\code{"cartesian"}, \code{"gnomonic"} or \code{"orthographic"}.
}
\item{grid}{logical. Whether the given coordinates are considered to
be on a grid given by \code{c(start, step, length)}.
Default: \code{FALSE}.
}
\item{...}{the optional arguments of \command{\link[stats]{dist}}
}
}
\details{
The functions transform between different coordinate systems.
}
\value{
The function \command{RMtrafo} returns a matrix, in general. For
fixed column,
the results, applied to each row of the matrix, are returned.
The function \command{RFearth2cartesian} returns a matrix in
one-to-one correspondence with \code{coord} assuming that the
earth is an ellipsoid.
The function \command{RFearth2dist} calculates distances, cf.
\command{\link[stats]{dist}}, assuming that the
earth is an ellipsoid.
}
\references{
For calculating the earth coordinates as ellipsoid:
\itemize{
\item \url{https://en.wikipedia.org/wiki/Geographic_coordinate_system}
\item \url{https://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html}
}
}
\note{
Important options are \code{units} and \code{coordinate_system}, see
\command{\link{RFoptions}}.
Note also that the zenit must be given explicitly for projection onto
a plane. See the examples below.
}
\me
\seealso{
\link{constants},
\command{\link{RMangle}},
\command{\link{RMid}},
\command{\link{RMidmodel}}.
}
\examples{\dontshow{StartExample()}
data(weather)
(coord <- weather[1:5, 3:4])
(z <- RFfctn(RMtrafo(new=RC_CARTESIAN_COORD), coord))
(z1 <- RFearth2cartesian(coord)) ## equals z
z1 - z ## 0, i.e., z1 and t(z) are the same
dist(z)
(d <- RFearth2dist(coord))
d - dist(z) ## 0, i.e., d and dist(z) are the same
## projection onto planes
RFoptions(zenit=c(-122, 47))
RFearth2cartesian(coord, system="gnomonic")
RFearth2cartesian(coord, system="orthographic")
\dontshow{\dontrun{ # OK
## RFearth2dist is more precise !!!
library("fields")
(system.time(z2 <- rdist.earth(coord, miles=FALSE)))
z2
(z2 - as.matrix(d)) / z2 * 100 ## RFearth2dist is more precise
#
n <- 10000
system.time(for (i in 1:n) d <- RFearth2dist (coord))) ## the same as dist(t(z))
system.time(for (i in 1:n)z2 <- rdist.earth(xx)))
data(weather)
xx <- matrix(weather[, 3:4], ncol=2) [ 1:5, ]
xx <- weather[, 3:4][ 1:5, ]
Print(xx)
Print(yy <- RFfctn(RMtrafo(new=RC_CARTESIAN_COORD), xx), units="miles")
(z1 <- as.matrix(dist(t(yy))))
library(fields)
(z2 <- rdist.earth(xx))
(z1-z2) / z1 * 100
z1
}}
\dontshow{FinalizeExample()}}
\keyword{spatial}
\keyword{models}
|
