A Compass can be defined as a device or a calibrated instrument used to identify the geographical direction of the earth’s North and South poles. The calibration on it indicates the direction of the geomagnetic North, South, East and West pole with the help of it’s free moving magnetic needle pointer.
Another name for a compass is called a ROSE of the WIND or WINDROSE.
Therefore, as an Install, knowing the direction in which the Dish will face before starting installation is very important and with the use of a compass, when placed on a hand would naturally indicate or point to the North cardinal pole direction then from the North position, you can determine the South, in the opposite direction, East at the right and West at the left.
Another way to determine your East Cardinal Point is to notice or observe the direction of rising of the Sun then, from there, every other position would be fished out.