Place an object of known dimensions, like a rectangle of plywood or foam core, or whatever, the larger the better, standing up against the pole or wall. Take a picture of the sign, the wall or pole,and your reference rectangle. Try to shoot the picture as straight on as possible as well as from the ground to the top of the sign. Import the picture into whatever whatever you're using [Flexi, Adobe, Corel, whatever]. Outline the reference object as accurately as you can. Map the photo into the outline object you drew. Manipulate the outline object into a rectangle of exactly the size of the reference object. Unmap the photo and you will have a full-scale picture of the sign and wall/pole. Take your measurements from that.