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...
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.
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.
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."
Comments
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...
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.
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.
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.
Calculus is basically algebra with a bigger vocabulary of operations.
Depends. Calculus deals with limits and integration. Algebra is more interested in how groups, rings and fields and other structures work.
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."
It's just a copy-paste of the equation from the Wikipedia article on the geoid: http://en.wikipedia.org/wiki/Geoid#Spherical_harmonics_repre...