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Whoa. That escalated fast. I thought I was reading an simple article about property data. And then, BOOM! All the sudden we're discussing file formats, and then

by choward 12y ago

Whoa. That escalated fast. I thought I was reading an simple article about property data. And then, BOOM! All the sudden we're discussing file formats, and then making database queries. And out of nowhere this monster appears: http://robrhinehart.com/wp-content/uploads/2015/01/spherical_harmonics.png http://robrhinehart.com/wp-content/uploads/2015/01/spherical...

tfgg 12y ago
That equation is rather unnecessary showing off, I don't see it being used later on, and the author doesn't bother trying to explain it. It looks like (going by the GM/r) that it might be the gravitational potential for a mass distribution described by a bunch of spherical harmonics.
- 7952 12y ago
  Yes, especially as one of the key advantages of using a projection is that you don't have to worry about this stuff. You can just work with a Cartesian coordinate system and the results will probably be right.
- johnloeber 12y ago
  The equation is barely even showing off: if you decode it, that's just a bunch of algebraic manipulations. There's not even any calculus in there.
  - nitrogen 12y ago
    Calculus is basically algebra with a bigger vocabulary of operations.
    - eru 12y ago
      Depends. Calculus deals with limits and integration. Algebra is more interested in how groups, rings and fields and other structures work.
zerocrates 12y ago
It's just a copy-paste of the equation from the Wikipedia article on the geoid: http://en.wikipedia.org/wiki/Geoid#Spherical_harmonics_representation http://en.wikipedia.org/wiki/Geoid#Spherical_harmonics_repre...
saraid216 12y ago
And immediately preceding that equation is this sentence: "If it sounds simple, it is not, but if you’re interested it’s a great reason to learn spherical harmonics." The entire point of showing off that equation is to say "This stuff is actually really deep and complicated and it's a rich subject to dive into on its own if you want to go for that, but I'm not going that route."

by choward 12y ago

tfgg 12y ago

That equation is rather unnecessary showing off, I don't see it being used later on, and the author doesn't bother trying to explain it. It looks like (going by the GM/r) that it might be the gravitational potential for a mass distribution described by a bunch of spherical harmonics.

7952 12y ago
Yes, especially as one of the key advantages of using a projection is that you don't have to worry about this stuff. You can just work with a Cartesian coordinate system and the results will probably be right.
johnloeber 12y ago
The equation is barely even showing off: if you decode it, that's just a bunch of algebraic manipulations. There's not even any calculus in there.
- nitrogen 12y ago
  Calculus is basically algebra with a bigger vocabulary of operations.
  - eru 12y ago
    Depends. Calculus deals with limits and integration. Algebra is more interested in how groups, rings and fields and other structures work.

zerocrates 12y ago

It's just a copy-paste of the equation from the Wikipedia article on the geoid: http://en.wikipedia.org/wiki/Geoid#Spherical_harmonics_representation http://en.wikipedia.org/wiki/Geoid#Spherical_harmonics_repre...

saraid216 12y ago

And immediately preceding that equation is this sentence: "If it sounds simple, it is not, but if you’re interested it’s a great reason to learn spherical harmonics." The entire point of showing off that equation is to say "This stuff is actually really deep and complicated and it's a rich subject to dive into on its own if you want to go for that, but I'm not going that route."