at front of,at the front of,和in front of,in the front of四者之间有什么区别和联系

in front of在…前面，如：
There is a tree in front of the house.房子前面有一棵树。
He sits in front of me.他坐在我前面。
in the front of 在…前部(在某范围以内)
如：There is a big desk in the front of the classroom. It's for the teacher.
教室的前部有一张大桌子，是老师用的。
(在教室范围里面)
at the front of 在…前部与in the front of同意
at…强调“前部的某一点” in强调在…范围的前部
如：There is a man boating at the front of the boat.船的前部有一个人在划船