My Math Forum  

Go Back   My Math Forum > High School Math Forum > Algebra

Algebra Pre-Algebra and Basic Algebra Math Forum


Reply
 
LinkBack Thread Tools Display Modes
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?
rich2020 is offline  
 
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)
dextrous is offline  
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?
rich2020 is offline  
February 4th, 2012, 12:34 PM   #4
Newbie
 
Joined: Feb 2012

Posts: 5
Thanks: 0

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? :/
rich2020 is offline  
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.
dextrous is offline  
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.
rich2020 is offline  
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.
rich2020 is offline  
Reply

  My Math Forum > High School Math Forum > Algebra

Tags
calculate, circle, coordinates, point



Thread Tools
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
calculate coordinates clankill3r Algebra 2 October 11th, 2012 06:05 PM
calculate the coordinates of the image P' of the point (3;5) joker91 Algebra 6 May 25th, 2012 04:56 AM
Calculate coordinates clankill3r Algebra 2 October 20th, 2011 03:00 PM
Calculates the coordinates of point P. condemath Calculus 1 August 16th, 2011 02:57 PM
Solved|Finding coordinates of a point in a circle with angle AlicanC Algebra 1 August 6th, 2008 01:51 AM





Copyright © 2019 My Math Forum. All rights reserved.