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April 5th, 2013, 12:23 AM  #1 
Newbie Joined: Apr 2013 Posts: 1 Thanks: 0  Closest Point of Approach (CPA) mathematical formula
Hello guys, I recently searching for mathematical formula to find closest point of approach (CPA) to be applied to my radar ship program and I can't find the correct ways to calculates it. anybody know what are the correct formula besides plotting in manually? any mathematical formula or coding? thank you very much for anyone that help me. sorry for my bad english. 
April 5th, 2013, 01:08 PM  #2 
Global Moderator Joined: May 2007 Posts: 6,613 Thanks: 617  Re: Closest Point of Approach (CPA) mathematical formula
If you have an analytic expression for the distance as a function of time, you could use elementary calculus. This means finding the first derivative and set it equal to 0, etc.

April 5th, 2013, 06:36 PM  #3 
Senior Member Joined: Aug 2008 From: Blacksburg VA USA Posts: 338 Thanks: 4 Math Focus: primes of course  Re: Closest Point of Approach (CPA) mathematical formula
okay, I stole data essentially from a post a few back (http://www.mymathforum.com/viewtopic.php?f=27&t=39466 see this next link, it shows sample trajectories you can practice on. As per mathman, they stem from analytical functions, so you can create the "difference" function to differentiate etc. https://docs.google.com/spreadsheet/...lE&usp=sharing If the link doesn't work, I'll try to post a PNG 

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approach, closest, cpa, formula, mathematical, point 
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