During an ARPA operation, how can you confirm a target's course alteration?

To confirm a target's course alteration during an ARPA (Automatic Radar Plotting Aids) operation, one can effectively interpret the data from the history display. The history display on an ARPA system provides a graphical representation of a target's previous positions over time, showing its past track and any course changes that have occurred. By analyzing this data, mariners can ascertain whether the target has altered its course, as the display illustrates the trajectory that the vessel has followed.

This method is reliable because it utilizes the system's historical tracking capabilities, which are designed specifically to assist navigators in making informed decisions based on actual movement rather than assumptions or immediate visual observations. It allows for a more precise understanding of the target's movement patterns and trends compared to relying solely on visual observations, which may not always be accurate due to visibility conditions or the observer's position. Additionally, unlike requesting a status report from the target vessel, which may not always yield timely or accurate information, or using automatic tracking features that could be subject to errors, the history display provides concrete data that can be analyzed for thorough situational awareness.