finding the biggest posible rectangle inside a quadrilateral

Hi (first time poster),

This problem comes up at work from time to time. I'm hoping to find a simple technique for finding the answer.

We construct various outdour sport surfaces, tennis courts running tracks...

Every once in a while we get a slab of ashphalt in the form of a quadrilateral without any right angles and no parallel lines.. Our job is to find the biggest posible rectangle in the form width (x) length 2x inside this form. Is there a formula to find the placement of the rectangle?