#### tony873004

Science Advisor

Gold Member

- 1,749

- 141

From http://en.wikipedia.org/wiki/Oblate_spheroidal_coordinates I'm given the formulas to compute cartesian coordinates from oblate spheroidal coordinates.

[tex]

\begin{array}{l}

x = a\cosh \mu \,\,\cos \nu \,\,\cos \phi \\

y = a\cosh \mu \,\,\cos \nu \,\,\sin \phi \\

z = a\cosh \mu \,\,\sin \nu \\

\end{array}

[/tex]

But I've got a few questions:

I've written a short block of code to plot an oblate spheroid:

Code:

```
mu = 0.5
For a = 0 To 100
For nu = 0 To (2*pi) Step 0.02
For phi = 0 To (2*pi) Step 0.02
x = a * cosh(mu) * Cos(nu) * Cos(phi)
y = a * cosh(mu) * Cos(nu) * Sin(phi)
z = a * sinh(mu) * Sin(nu)
Call PlotPoint(x, z)
Next phi
Next nu
Next a
```

*μ*? I don't see it defined on Wikipedia's page. I image it is a number that describes how oblate the object is. So I imagine there should be a number I can set it to that gives me a sphere. My guess would be that mu can range from 0 to 1, with one of those limits giving me a sphere.

So I tried it. I see that

*μ*= 0 gives me a straight line, meaning completely oblate, and the larger I set this number, the more spherical the shape becomes. But it seems to become a sphere at

*μ*= 2, contrary to my guess. Any value larger than 2 gives me a larger sphere. Does anyone know exactly what

*μ*is, and what it's range is?

Also, I see Earth described as an oblate spheroid. What is its

*μ*value?

Thanks!!