geetrue,
Right you are. As far as I know, the form was originally used for plotting target information transferred from the radar scope.
In my case, I plot the tagets relative position and movement; based on observations of time, bearing, and range with the UZO or periscope.
By the way, this is a pretty good tool for teaching a budding navigator a little applied geometry and trig. See this post:
http://www.subsim.com/radioroom/show...53&postcount=1