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+.TH LIBTELLURIAN 7 libtellurian
+.SH NAME
+libtellurian \- Geodesy library
+
+.SH SYNPOSIS
+.ni
+#include <libtellurian.h>
+.fi
+.PP
+Link with
+.I -ltellurian
+.IR -lm .
+
+.SH DESCRIPTION
+.B libtellurian
+provides a collection of geodesy functions
+and constants.
+.PP
+.B libtellurian
+always uses meters as the length unit,
+meters per square-second as the acceleration unit,
+and degrees for the angle unit, except when the
+function name uses the suffix \(dq_radians\(dq, in which
+case the function uses radians instead of degrees.
+All functions that input or output angles have a
+version that uses degress and a version that uses
+radians. Unless otherwise specified, functions that
+use degress convert the input and output to and from
+radians and call the version of the function that
+uses radians.
+.PP
+.B libtellurian
+provides the following functions (with some similar
+alternatives described in these functions' man pages):
+.PP
+.I Altitude calculation
+.TP
+.BR libtellurian_sea_level (3)
+Calculate distance the centre of the Earth and a
+point on the ellipsoid (reference datum for raw GPS
+altitude).
+.PP
+.I Distance and direction calculation
+.TP
+.BR libtellurian_coarse_distance (3)
+Calculate an approximate distance between two
+points the on ellipsoid of the Earth. This is a
+very cheap operation that is useful to filter out
+points from a large collection to find the closest
+ones.
+.TP
+.BR libtellurian_distance (3)
+Calculate an accorate distance between two
+points the on ellipsoid of the Earth, as well
+as the forwards azimuths.
+.PP
+.I Travel projection
+.TP
+.BR libtellurian_end_point (3)
+Calculate where a traveller will end up after
+travelling for some distance in some direction.
+.PP
+.I Gravity calculation
+.TP
+.BR libtellurian_normal_gravity (3)
+Calculate the normal gravity for some point on
+the Earth's ellipsoid.
+.TP
+.BR libtellurian_elevated_gravity (3)
+Adjust a gravity for some ellipsoidal height.
+.PP
+.I Radius of curvature calculation
+.TP
+.BR libtellurian_meridan_radius (3)
+Calculate the Earth's meridan radius of
+curvature for some latitude.
+.TP
+.BR libtellurian_transverse_radius (3)
+Calculate the Earth's transverse radius of
+curvature for some latitude.
+.TP
+.BR libtellurian_azimuthal_radius (3)
+Calculate the Earth's azimuthal radius of
+curvature for some latitude and azimuth.
+.TP
+.BR libtellurian_gaussian_radius (3)
+Calculate the Earth's Gaussian (non-directional)
+radius of curvature for some latitude.