On a marine Radar device how would the display indicate a change in course or speed by a target vessel?

Question

On a marine Radar device how would the display indicate a change in course or speed by a target vessel?

Answer 1

Before you can determine a course or speed change in a target, you must first determine the initial true course and speed of the target, by subtracting out your own vessel's course and speed (radar displays relative motion), and then predicting where that will be at specific intervals in the future. If you have not changed course and speed and the target does not end up where you expected it to be when you expected it to be, the target has maneuvered, and you have to start the process all over again. Once upon a time when the world was young and dinosaurs roamed the earth, we did this with grease pencil right on the radar screen; nowadays we have computers built into the radar that do most of the work for us. It's called ARPA (automated radar plotting aid), and it's an excellent tool, but still prone to the same errors that a person plotting with a grease pencil would be.

Answer 2

If your unit has the software to select and isolate a target and report on changes then the answer is - 'yes'  Otherwise, you will have to watch the screen and pay attention to the movements of any targets that appear.