% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/tidal_correction.R
\name{.nodal_factors}
\alias{.nodal_factors}
\title{Compute Schureman nodal amplitude (f) and phase (u) corrections}
\usage{
.nodal_factors(t_mean)
}
\arguments{
\item{t_mean}{POSIXct. Representative timestamp for the survey (typically
the midpoint of the survey period). Nodal factors vary over months, so
a single midpoint evaluation is accurate to well within the constituent
uncertainty budget.}
}
\value{
Named list with elements \code{f} and \code{u}, each a named numeric vector
indexed by constituent name (M2, S2, N2, K1, O1).
}
\description{
Computes the 18.6-year lunar nodal modulation factors f (amplitude scale)
and u (phase correction in degrees) for M2, S2, N2, K1, O1 at a given epoch.

Formulae from Schureman (1940) Tables 2 & 3; same as those used by
UKHO, NOAA, and most modern tidal prediction software.
}
\keyword{internal}
