Circle and hexagon are in separate plane. Hexagon plane is active. Clicking point1 and point2 gives dimension between graphic area center point and hexagon center point.
How to explain this?
I would hazard a guess that the circle on the other plane is concentric with the origin. Try viewing your current sketch "Normal to" & see if the circle appears at the origin.
Yes circle is concentric to origin.
Now circle is away from graphical area origin. Same action is giving another dimension. What is this dimension?
I assume this dimension is a shortest distance between projected circle center point on the hexagon plane and hexagon center point.
I believe anytime you dimension a sketch on one plane, to a sketch in another you will get a similar result. Unless you are in a 3d sketch, SW will translate the point you have selected from the other sketch (or geometry) onto the working plane. You will get the same result if you add a linear sketch to the plane below and try dimensioning to a corner. In your example it just happens that the circle is concentric to the origin and therefore it appears to dimension to the origin. however if you were to edit the circular sketch so it was no longer concentric to the origin I think you'll find the dimension will move off the origin also.
The dimension will will always lie on the plane that the sketch is on, so like Bjorn said, since the origin of the circle is on the origin of the part in the X-Y plane, when you dimension it will go from the center point of the circle as it is translated to the plane you are on to the center of the hex, which is what it did. It's similar to projecting a point or line onto a surface.
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