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Last Post:
11May2011 21:58
by: cmasters2002



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Calculate intersection of 2 points
Posted:
09May2011 08:51


Hi all
I have 2 OS grid ref's with bearing's coming from them, I need to calculate a 3rd point(intersection of bearing's from point 1,2) to place a marker on a map but cannot figure out how to calculate the 3rd point
EG
Point 1  E391300 N157935 bearing 130 deg Point 2  E391850 N151560 beaing 45 deg Pont 3 ????
Could anyone teLl me how to calculate point 3 or point me in the right direction
Thanks
Colin


Posts:
390
Registered:
07/02/08



Re: Calculate intersection of 2 points
Posted:
10May2011 13:17
in response to: cmasters2002


You can use simple trig


Posts:
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Re: Calculate intersection of 2 points
Posted:
10May2011 18:01
in response to: chadwickBill


Trig may be simple to some people but not to me
Could you give me an example of how to do this with trig
thanks
colin


Posts:
390
Registered:
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Posts:
390
Registered:
07/02/08



Re: Calculate intersection of 2 points
Posted:
11May2011 20:02
in response to: chadwickBill


Actually this might be more helpfull to you
http://en.wikipedia.org/wiki/Triangulation
You can use OpenLayers.Geometry.Point.distanceTo to get the distance between your two points.


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Re: Calculate intersection of 2 points
Posted:
11May2011 20:24
in response to: chadwickBill


and
dx = eastings1  eastings2; dy = (northings1  northings2); // allow for north increasing up bearing = (Math.atan2(dy, dx) * 180.0 / Math.PI)  90.0;
to find the compass bearing in degrees between your two points and so two of the angles of your triangle.
Then as you know two angles and one side ...
http://oakroadsystems.com/twt/solving.htm


Posts:
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Registered:
28/11/09



Re: Calculate intersection of 2 points
Posted:
11May2011 21:58
in response to: chadwickBill


Hi as mentioned I am certainly know maths expert, and am a bit unsure at what you are getting at?
if possible could you elaborate more on your answer as I know the XY of point 1 and 2 and also the bearings from north. I need to calculate the intersecion of the projected lines from the bearings of both points and return point 3
thanks
colin



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