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Algorithm

I learned (and subsequently forgot) only one computer language in school: Fortran. Fortran 77, folks. I'm sure Fortran was really cool back in 1892 when it was the First Programming Language Ever, but I hate it. But while I didn't like writing the actual code, I really enjoyed coming up with the algorithms. I like trying to think like that, figure out how stuff works, break things down to their basics.

ANYWAY, I'm supposed to be delineating drainage areas on this site map -- you know, figuring out where all the water will go when it rains. But it's hard to visualize, and when I get stuck my mind wanders and I start thinking of an algorithm for a program that will delineate drainage areas FOR me.

Comments

( 10 comments — Leave a comment )
qed
Jan. 31st, 2002 01:42 pm (UTC)
.
Algorithms are the most wonderful combination of mathematical, formal reasoning with intuition and problem solving.

And, if you remember enough Calc. III, a numerical gradient calculation would do your drainage problem for you, assuming you can get elevation information from the map.
littlewashu
Jan. 31st, 2002 01:47 pm (UTC)
That's a big "if" . . .

Of course I can get elevation information! How do you think I'm doing it?

I'm also pretty sure AutoCAD Land Development does it, but they don't have that kind here.
rhino777
Jan. 31st, 2002 02:00 pm (UTC)
don't know if this helps or not but this looks neat gis stuff
qed
Jan. 31st, 2002 06:16 pm (UTC)
.
I remember looking at their stuff when I needed an ADRG map reader... they do some neat shit. TerraServer is also cool, and free.
slickninja
Jan. 31st, 2002 06:16 pm (UTC)
I wish I had your skillz. All I learned was C and as it turns out my entire master's thesis revolves around a FORTRAN program that was written in 1978. It's older than me!
apeth
Jan. 31st, 2002 11:10 pm (UTC)
i wish i was studying math that had numbers yet (numbers that aren't just a different type of line, anyway.)

i know generally, but what specifically makes an algorithm an algorithm, as opposed to an equation? and doesn't water just go down until it fills up something?
littlewashu
Feb. 1st, 2002 06:21 am (UTC)
answers
Man, the more you learn about math, the less numbers you use. Except for . . . I think . . . Linear Algebra? I never took that.

Okay, an algorithm isn't an equation at all. It's like . . . a plan for the program, but you're not writing the actual code. You say, "okay, first I'll identify the greatest number in this set, and then I'll throw in an if-then statement . . ," shit like that. You write your program based on the algorithm. Or maybe you're supposed to write a flow chart based on the algorithm, and then the code based on the flow chart? Like I said, I only took one course (well, one language, I took two semesters of it) and that was five years ago, so some current computer geek might correct me a little, but that's the general gist of it.

And . . . yes, young man, water does go down. I have to draw little lines around the high points, so that I can pick any point on the plan and say "this drop of water will eventually end HERE," with "here" generally being an inlet or a basin or some other water-collecting mechanism.

I hope you were really asking these questions for real, otherwise I'll feel foolish.
apeth
Feb. 1st, 2002 09:54 am (UTC)
Re: answers
ah...cool, that makes sense. Now if it can only be used to help figure out Apollonius' conic sections, then I'll have some serious intellectual victory.

and yeah, those were honest questions. I go to a weird school- last semester i finished doing Ptolemaic Astronomy and now we're doing conic geometry, which means hyperbolae and parabolae and ellipses, but only talking about them through ratios and geometric lines and occasionally if we're lucky a semicircle. This makes it interesting to try and map them out, to say the least, especially because we don't have a coordinate system yet.

qed
Feb. 1st, 2002 06:57 am (UTC)
An algorithm is a step-by-step process for doing something. For example, an algorithm for finding the largest number in a list:

1. Start at the beginning of the list. Write down the 1st number.
2. For every number in the list, if that number is larger than the one you've written down, erase the one you wrote down and write this new largest number.
3. After going through all numbers in the list, the number you have written down is the largest number.

apeth
Feb. 1st, 2002 09:45 am (UTC)
Re:
ah-ha. cool.
( 10 comments — Leave a comment )

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