It appears it simplifies measuring length by triginometry. You have to measure the first length you want and set the laser till it points at the end of the log and the down angle is set at that point then make a cut or mark. Move down the log and when the laser touches the cut or mark you just made then the length is the same as the first cut. Make a mark or cut and repeat. Imagine the log is the base or a right triangle, the laser line is the hypotenuse side of the triange.
Steve
That's what I was thinking.
The problem I see is consistently getting the saw body perpendicular to the log. Large bark or bumps can change the angle of the saw, which changes the length measured.