Virtual Fence Maker

It is often required for local cameras to detect objects when they are inside the speficic area which is already set like a fence. If this area is circle, this will be projected in local cameras as a ellipse shape. So, this area can be masked as an image for this kind of detection. However, the problem is that the center of circle is able to be
not only on the ground but also
over the ground. Therefore, the circle area should be projected on the ground because objects which are inside this fence go around on the ground.
Requirement
Getting the Fence Mask

For the More Accurate Ellipse Mask
emoy.net