other common codes are
mirror - your mirror is the bunker in the same position as yours on the other side of the field so if i was stood in back left my mirror would be the back left as i look down the field
opposite - your opposite is the bunker opposite yours on field, so i was back left my opposite would be in the corner diagonal to mine, ie back right
center - dead simple its the bunker in the middle of the field, usually the one with the flag on it and where the bunker monkeys break out to!
codes for different sort of bunkers - coke cans, tea bags, wing nuts .....just basic descriuptions of the shapes of the bunkers.
complex - a group of bunkers usually touching each other
hot - a bunker that is hot is one that has an opposition player in it
what ever works best for your team really...but above all else keep it simple...you dont want to have to sit there trying to decode stuff when you should be shooting fools