Find a geo-location (lat,lon) according to distance to three reference points?

I am trying to find a point on earth in Latitude/Longitude. I do know three reference points and the respective distance from each of these reference points to the searched for point.





The idea is that the intersections of two circles would return two potential canditates for the point I am looking for. Using the third reference point/circle I should then be easily able to determine which of the two canditates is the point I am looking for.


I first tryed to find a solution using algebra until I realised that the circle forumla does not work for latitude/longitude because the radius/distances do not match.





Trying an algorithmic approach I am stuck at finding the intersection of two circles. I can find any points lieing on one particular circle but I cant seem to find a way to _RELIABLY_ find an intersection of two circles.


I also must have a limited number of iterations, e.g. a resource friendly way of finding the intersection.





Any idea or help is greatly appreciated

Find a geo-location (lat,lon) according to distance to three reference points?
Or, here's what you can do, use Google Earth, download here:


http://www.earth.google.com


if you don't have it yet. Than use the ruler which is located at the program's upper toolbar. Click one reference point on and draw the exact distance out to where you are approximately going (toward the center of the 3 points).


Doing this with all three of your reference points, the exact measured distances from each reference point will lead you to your geographic location, since you will be able to draw imaginary circles that way.


This eliminates the impossible algebraic work with the oddity of the longitude/latitude division in 60 instead of 100 units in a whole.


Good luck!!





So, If I understood right, the geographical coordinates of latitude and longitude are no subject in your question? But even so, you should be able to locate your point-to-find with the Google Earth ruler by using it from each reference point and see where those lines will intersect. They have to intersect, since you have THREE reference points, not only two!
Reply:Find and download a program called "corpscon". This will convert geodetic coordinates (latitude %26amp; longitude) to local plane coordinates. After this conversion, use your distance in feet or meters whichever you have converted to to draw your circles. After determining the local plane coordinates, you can use the corpscon program to convert them back to geodetic.

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