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	geodetic( deg2rad( -40 ), deg2rad( 105 ), 0 )->eci( $time );

    tolerance_frac( $x, -1703.295, 1e-6, 'Geodetic to ECI: X' );

    tolerance_frac( $y, -4586.650, 1e-6, 'Geodetic to ECI: Y' );

    tolerance_frac( $z, -4077.984, 1e-6, 'Geodetic to ECI: Z' );
}


# eci -> geodetic
# Tests: eci() (and geodetic() and geocentric())

# This is the reverse of the previous test.

{
    my $time = greg_time_gm( 0, 0, 9, 1, 9, 1995 );

    my ( $lat, $long, $elev ) =
	Astro::Coord::ECI->new( ellipsoid => 'WGS72' )->
	eci( 1703.295, 4586.650, 4077.984, $time )->geodetic();

    tolerance_frac( $lat, deg2rad( 40 ), 1e-6,
	'ECI to geodetic: latitude' );

    tolerance_frac( $long, deg2rad( -75 ), 1e-6,
	'ECI to geodetic: longitude' );

    $elev += EQUATORIALRADIUS;
    tolerance_frac( $elev, EQUATORIALRADIUS, 1e-6,
	'ECI to geodetic: distance from center' );

    $time = greg_time_gm( 0, 0, 9, 1, 9, 1995 );

    ( $lat, $long, $elev ) =
	Astro::Coord::ECI->new( ellipsoid => 'WGS72' )->
	eci( -1703.295, -4586.650, -4077.984, $time )->geodetic();

    tolerance_frac( $lat, deg2rad( -40 ), 1e-6,
	'ECI to geodetic: latitude' );

    tolerance_frac( $long, deg2rad( 105 ), 1e-6,
	'ECI to geodetic: longitude' );

    $elev += EQUATORIALRADIUS;
    tolerance_frac( $elev, EQUATORIALRADIUS, 1e-6,
	'ECI to geodetic: distance from center' );
}


# azel
# Tests: azel() (and geodetic(), geocentric(), and eci())

# Book solution from
# http://www.satcom.co.uk/article.asp?article=1

note <<'EOD';

In the following three tests the tolerance is degraded because the
book solution is calculated by http://www.satcom.co.uk/article.asp?article=1
which apparently assumes an exactly synchronous orbit. Their exact
altitude assumption is undocumented, as is their algorithm. So the
tests are really more of a sanity check.

EOD

{
    my $time = greg_time_gm( 0, 0, 5, 27, 7, 2005 );
    my $sta = Astro::Coord::ECI->new( ellipsoid => 'GRS80' )->
	geodetic( deg2rad( 38 ), deg2rad( -80 ), 1 );
    my $sat = Astro::Coord::ECI->new( ellipsoid => 'GRS80' )->
	universal( $time )->
	geodetic( deg2rad( 0 ), deg2rad( -75 ), 35800 );

    my ( $azm, $elev, $rng ) = $sta->azel( $sat );

    tolerance_frac( $azm, deg2rad( 171.906 ), 1e-3,
	'Azimuth for observer' );

    tolerance_frac( $elev, deg2rad( 45.682 ), 1e-3,
	'Elevation for observer' );

    tolerance_frac( $rng, 37355.457, 1e-3,
	'Range for observer' );

    # Same as above tests, but with the station in the 'station'
    # attribute.

    $sat->set( station => $sta );

    ( $azm, $elev, $rng ) = $sat->azel();

    tolerance_frac( $azm, deg2rad( 171.906 ), 1e-3,
	'Azimuth for observer' );

    tolerance_frac( $elev, deg2rad( 45.682 ), 1e-3,
	'Elevation for observer' );

    tolerance_frac( $rng, 37355.457, 1e-3,
	'Range for observer' );

    # enu
    # Tests: enu()

    # From the azel() test above, converted as described at
    # http://geostarslib.sourceforge.net/main.html#conv

    my ( $East, $North, $Up ) = $sat->enu();

    tolerance( $East, 3675, 10,
	'East for observer' );

    tolerance( $North, -25840, 10,
	'North for observer' );

    tolerance( $Up, 26746, 10,
	'Up for observer' );
}

# atmospheric refraction.
# Tests: correct_for_refraction()