Answered: 9 Jan 2006 at 1:46:41 AM
Dear Andy,
In order to measure the direction of the main door, you will need to measure it at the main door facing out. You can also stand outside the house and line it up by facing the door but you will need to be very accurate. This will negate the interferenc of any electro magnetic inteference. In order to measure the location of the door, you then measure from the centre of the house.
Regards
Di