Numerical Examples for Miller Cylindrical Projection #
SPHERE #
Forward Equations #
Given
Radius of sphere: | $R=\;\;$ unit |
Central meridian: | $\lambda_0=\;$° |
Point: | $\phi=\;$° |
$\lambda=\;$° | |
Using equations (11-1) through (11-5) in order
$$ \DeclareMathOperator{\arcsinh}{arcsinh} $$
$$
\eqalign{
x &= 1.0\times[-75^\circ-0^\circ]\times\pi/180^\circ \cr
&= -1.3089969\;\text{units}
}
$$
$$
\eqalign{
y =& 1.0\times[\ln{\tan(45^\circ+0.4\times50^\circ)}]/0.8 \cr
=& (\ln{\tan 65^\circ)}/0.8 \cr
=& 0.9536371\;\text{units}
}
$$
or$$
\eqalign{
y &= 1.0\times\{\arcsinh[\tan(0.8\times50^\circ)]\}/0.8 \cr
&= 1.0\times\arcsinh{0.8390996}/0.8 \cr
&= 0.9536371\;\text{units}
}
$$
$$
h = \sec(0.8\times50^\circ) = 1/\cos40.0000000^\circ = 1.3054073
$$
$$
k = \sec50^\circ = 1/\cos50^\circ = 1.5557238
$$
$$
\eqalign{
\sin{1/2\omega} &= [\cos(0.8\times50^\circ) - \cos50^\circ]/[\cos(0.8\times50^\circ) + \cos50^\circ] \cr
&= 0.0874887
}
$$
$$
\omega=10.0382962^\circ
$$
Inverse Equations #
Inversing forward example:
Given: $R, \lambda_0$, for forward example
$x=\;$ units |
$y=\;$ units |
Using equations (11-6) and (11-7),
$$
\eqalign{
\phi &= 2.5\arctan \mathrm{e}^{0.8\times0.9536371/1.0}-(5\pi/8)\times180^\circ/\pi \cr
&= 2.5\arctan \mathrm{e}^{0.7629097} - 1.9634954\times180^\circ/\pi \cr
&= 2.5\arctan (2.1445070) - 1.9634954\times180^\circ/\pi \cr
&= 2.5\times65.0000006^\circ - 112.5000000^\circ \cr
&= 50.0000015^\circ
}
$$
or$$
\eqalign{
\phi &= \arctan[\sinh(0.8\times(-0.8428443)/1.0)]/0.8 \cr
&= \arctan (-0.7265425)/0.8 \cr
&= -44.9999978^\circ
}
$$
$$
\eqalign{
\lambda &= -5^\circ + (-1.2217305/1.0)\times 180^\circ/\pi \cr
&= -5^\circ + (-70.0000014^\circ) \cr
&= -75.0000014^\circ
}
$$