Numerical Examples for Sinusoidal Projection #
SPHERE #
Forward Equations #
Given
Radius of sphere: | $R=\;\;$ unit |
Central meridian: | $\lambda_0=\;$° |
Point: | $\phi=\;$° |
$\lambda=\;$° | |
From equations (30-1) through (30-5) in order,
$$
\eqalign{
x &= 1.0\times[-75^\circ-(-90^\circ)]\cos(-50^\circ) \cr
&= 0.1682814\text{ units}
}
$$
$$
\eqalign{
y &= 1.0\times(-50^\circ)\times\pi/180^\circ \cr
&= -0.8726646\text{ units}
}
$$
$$
\eqalign{
h &= \{1+ [-75^\circ-(-90^\circ)]^2\times(\pi/180^\circ)^2\times\sin^2(-50^\circ) \}^{1/2} \cr
&= 1.0199119
}
$$
$$
\eqalign{
k &= 1.0
}
$$
$$
\eqalign{
\theta' &= \arcsin(1/1.0199119) \cr
&= 78.6597719^\circ
}
$$
$$
\eqalign{
\omega &= 2\arctan[(1/2)[-75^\circ-(-90^\circ)]\times(\pi/180^\circ)\times\sin(-50^\circ)] \cr
&= 11.4523842^\circ
}
$$
Inverse Equations #
Inversing forward example:
Given: $R, \lambda_0$, for forward example
$x=\;$ units |
$y=\;$ units |
From equations (30-6) and (30-7),
$$
\eqalign{
\phi &= (-0.8726646/1.0)\times180^\circ/\pi \cr
&= -49.9999985^\circ
}
$$
$$
\eqalign{
\lambda &= -85^\circ+0.1682814/[1.0\cos(-49.9999985^\circ)]\times180^\circ/\pi \cr
&= -70.0000007^\circ
}
$$
ELLIPSOID #
Forward Equations #
Given
ellipsoid | $a=$ | 6378206.4 m |
$e^2=$ | 0.00676866 | |
Central meridian: | $\lambda_0=$ | ° |
Point: | $\phi=$ | ° | $\lambda=$ | ° |
Using equations (30-8), (3-21), and (30-9) in order,
$$
\eqalign{
x =& 6378206.4\times[-75^\circ-(-90^\circ)]\times(\pi/180^\circ)\cos(-50^\circ)/ \cr
& [1-0.0067687\sin^2(-50^\circ)]^{1/2} \cr
=& 1075471.54\text{ m}
}
$$
$$
\eqalign{
M =& 6378206.4\times[(1-0.0067687/4-3\times0.0067687^2/64 \cr
& -5\times0.0067687^3/256)\times (-50^\circ)\times \pi/180^\circ \cr
& -(3\times0.0067687/8+3\times0.0067687^2/32 \cr
& +45\times0.0067687^3/1024)\times\sin(2\times(-50^\circ)) \cr
& +(15\times0.0067687^2/256+45\times0.0067687^3/1024) \cr
& \times \sin(4\times(-50^\circ)) -(35\times0.0067687^3/3072) \cr
& \times\sin(6\times(-50^\circ))] \cr
=& -5540628.03\;\text{m}
}
$$
$$
y = -5540628.03\text{ m}
$$
Inverse Equations #
Inversing forward example:
Given
$x=\;$m |
$y=\;$m |
Using equations (30-10), (7-19), (3-24), (3-26), and (30-11) in order,
$$
M = -5540628.03
$$
$$
\eqalign{
\mu =& -5540628.03 /[6378206.4\times(1-0.0067687/4 \cr
& -3\times0.0067687^2/64 - 5\times0.0067687^3/256)] \cr
=& -0.8701555 \;\text{radians} = -49.8562392^\circ
}
$$
$$
\eqalign{
e_1 &= [1-(1-0.0067687)^{1/2}]/[1+(1-0.0067687)^{1/2}] \cr
&= 0.001697916
}
$$
$$
\eqalign{
\phi =& -49.8562392^\circ+[(3\times0.0016979/2-27\times0.0016979^3/32)\sin(2\times(-49.8562392^\circ)) \cr
&+(21\times0.0016979^2/16-55\times0.0016979^4/32)\sin(4\times(-49.8562392^\circ)) \cr
&+(151\times0.0016979^3/96)\sin(6\times(-49.8562392^\circ)) \cr
&+(1097\times0.0016979^4/512)\sin(8\times(-49.8562392^\circ))]\times180^\circ/\pi \cr
=&-50.0000001^\circ
}
$$
$$
\eqalign{
\lambda =& -90^\circ+\{1075471.54\times[1-0.0067687\sin^2(-50.0000001^\circ)]^{1/2}/ \cr
& [6378206.4\cos(-50.0000001^\circ)]\}\times(180^\circ/\pi) \cr
=& -75^\circ
}
$$