Originally Posted by Hudsonian
I find the Davis One Arm Protractor easiest to use-- particularly, when at the helm I'm working with a chartbook in my lap. Parallel rulers, roller plotter, and a pair of triangles all require a flat surface.
and ideally charts without any creases or folds.
I have a Davis plotter as well. I like the sturdy construction of the Portland plotter and the ability of account for variation. I have some instructions that show how to account for deviation as well, but since none of the boats I sail have deviation cards, I have not tried out that feature.
The parallel rule is nice for doing a faster advanced LOP. But I am almost as fast with the Portland.
My next best "plotter" is the Douglas protractor. Not mentioned yet.