Finding a coordinate in a circle

Question

I am doing a mashup using Google Maps under Grails where users can create geofences by selecting a point on the map and a radius. This get stored on my database and the appl

Answer 1

Since you are using Google Maps and for geographical distances spherical geometry holds rather than euclidean geometry. However if it is relativley smaller distance like a parking lot etc. then you can use euclidean distance formula (http://en.wikipedia.org/wiki/Distance) to find out whether the point is inside or outside the circle.

I presume you know the coordinates of the circle's center C(xc, yc) and its radius, R. Then for a given point P(x1, y1) find the euclidean distance, D as

square-root((x1-xc)^2 + (y1-yc)^2)). If D > R, the point lies outside the circle. If D < R, the point lies inside the circle. If D = R, the point lies on the circumference of the circle.

In case you are doing your measurements over larger distances then you should rather look for Geodesics (please check this http://en.wikipedia.org/wiki/Great-circle_distance).

I hope it helps.

cheers