What is the grade line?
It is the line installed by the survey department so we the miners have a reference point that we can measure the distance to the floor and the backs and control the direction that we mine
There are two methods used to mark up grade lines underground. These are:
Using a string line requires two people if it is to be done accurately. The theory is simple, you string two lines across the drive that you line up to locate the grade at the face.
These lines are strung between survey points installed by the survey department.
Lasers are easy to use and is normally a one person job.
Place the laser in the unit in the wall, this will turn it on, this will shine a mark on the face that is the height of the grade line.
Approach the face and mark the spot with spray paint, then mark up your walls.