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 February 4th, 2012, 11:28 AM #1 Newbie   Joined: Feb 2012 Posts: 5 Thanks: 0 Calculate point coordinates within a circle Hi all, I am trying to figure out the coordinates of a point within a circle. I have an IR sensor which gives readings from 0 to 800. 800 meaning there are no objects in sight. What I want to do is make a miniture radar representation. I will have a turntable which will rotate the IR sensor while it scans for obstacles. Now, if it were a stationary IR sensor I'd know exactly where the object is - it would be whatever the sensor value returned because it would represent the Y axis... But, how would I work out the X and Y values for this point now that the IR sensor is rotating? I've drawn a diagram to help illustrate: Does anyone know the math to work this out? February 4th, 2012, 12:17 PM #2 Member   Joined: Feb 2012 Posts: 36 Thanks: 0 Re: Calculate point coordinates within a circle Convert the angle to radians and x=rcos(angle), y=rsin(angle) February 4th, 2012, 12:33 PM #3 Newbie   Joined: Feb 2012 Posts: 5 Thanks: 0 Re: Calculate point coordinates within a circle Ok, so after obtaining the X and Y, I could just subtract the distance of the object to the center from both values to give me the true value, correct? February 4th, 2012, 12:34 PM   #4
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Re: Calculate point coordinates within a circle

Quote:
 Originally Posted by rich2020 Ok, so after obtaining the X and Y, I could just subtract the distance of the object to the center from both values to give me the true value, correct?
I meant "distance of the object FROM the center of the circle" - can't edit posts? :/ February 4th, 2012, 12:38 PM #5 Member   Joined: Feb 2012 Posts: 36 Thanks: 0 Re: Calculate point coordinates within a circle Yep, basic coordinate pythagoras to locate the point in relation to the required limit of the sensor. February 4th, 2012, 12:39 PM #6 Newbie   Joined: Feb 2012 Posts: 5 Thanks: 0 Re: Calculate point coordinates within a circle Thanks very much for your help.  February 4th, 2012, 04:57 PM #7 Newbie   Joined: Feb 2012 Posts: 5 Thanks: 0 Re: Calculate point coordinates within a circle Hmm... I don't think your way was correct. I needed to find the coordinates based on the angle and the distance an object. What I did was: X=Cos(A) * Distance Y=Sin(A) * Distance I used degrees, not radians. Then, because my circle (radius of 15mm) will be far smaller as it will be on a mobile Android device's screen, I did this: Sensor range is 800mm... so X = X/(800/15) Y = Y/(800/15) Correct me if I'm wrong please. I need this for a software project. Tags calculate, circle, coordinates, point Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Threads Thread Thread Starter Forum Replies Last Post clankill3r Algebra 2 October 11th, 2012 06:05 PM joker91 Algebra 6 May 25th, 2012 04:56 AM clankill3r Algebra 2 October 20th, 2011 03:00 PM condemath Calculus 1 August 16th, 2011 02:57 PM AlicanC Algebra 1 August 6th, 2008 01:51 AM

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