.TH LIBTELLURIAN_SEA_LEVEL 3 libtellurian
.SH NAME
libtellurian_sea_level \- Calculate a geocentric radius

.SH SYNPOSIS
.nf
#include <libtellurian.h>

double libtellurian_sea_level(double \fIlatitude\fP);

double libtellurian_sea_level_radians(double \fIlatitude\fP);
.fi
.PP
Link with
.I -ltellurian
.IR -lm .

.SH DESCRIPTION
The
.BR libtellurian_sea_level ()
function calculates the distance from the centre of
the Earth the ellipsoid, for any point on the given
.IR latitude ,
which givens the nominal sea level at this position,
which is close to the actual sea level, and is the
reference datum for the altitude (ellipsoidal height)
reported in raw GPS measurements.
.PP
The
.I latitude
shall be specified according to GPS and in degrees.
.PP
The
.BR libtellurian_sea_level_radians ()
function is identical to the
.BR libtellurian_sea_level ()
function except that
.I latitude
shall be specified in radians.

.SH RETURN VALUE
The
.BR libtellurian_sea_level ()
and
.BR libtellurian_sea_level_radians ()
functions return the distance from the centre of
the Earth to the ellipsoid, measured in meters.

.SH ERRORS
None.

.SH NOTES
Some GPS systems, espcially those for hiking, surveying,
and aviation, report orthometric height (height above
sea level), rather than ellipsoidal height to make it
easier for the user to interpret.

.SH SEE ALSO
.BR libtellurian (7)