T90fromT68.Rd

\name{T90fromT68}
\alias{temperature conversion}
\alias{T90fromT68}
\alias{T68fromT90}
\alias{T90fromT48}

\title{Convert between temperature scales}

\usage{
T90fromT48(temperature)
T90fromT68(temperature)
T68fromT90(temperature)
}

\arguments{
    \item{temperature}{expressed in one scale}
}

\value{Temperature expressed in the second scale}

\description{Today's instruments typically record in the ITS-90 scale, but some
    old datasets will be in the IPTS-68 scale. \code{T90fromT68()} converts
    from the IPTS-68 to the ITS-90 scale, using Saunders' (1990) formula, while
    \code{T68fromT90()} does the reverse. The difference between IPTS-68 and
    ITS-90 values is typically a few millidegrees (see \sQuote{Examples}),
    which is seldom visible on a typical temperature profile, but may be of
    interest in some precise work.  Mostly for historical interest,
    \code{T90fromT48()} is provided to convert from the ITS-48 system to
    ITS-90.}

\examples{
library(oce)
T68 <- seq(3, 20, 1)
T90 <- T90fromT68(T68)
sqrt(mean((T68-T90)^2))
}

\references{P. M. Saunders, 1990. The international temperature scale of 1990,
    ITS-90.  WOCE Newsletter, volume 10, September 1990, page 10.
    (\url{http://www.nodc.noaa.gov/woce/wdiu/wocedocs/newsltr/news10/contents.htm})}