RADAR- Everyone knows when you use it but its accurate range and bearing data. Your platform must be surfaced to use it.
SONAR- Passive relies on TMA to generate a solution, all you can (mostly) rely on is semi-accurate bearing data and contact ID plus an accurate idea of speed based on blade count. Active is like RADAR, everyone knows you're out there.
Visual- Accurate bearing data plus limited range data plus relative target motion (which way are they pointed?) and identification. Limited to either on the surface or close to it. Mast can be spotted visually or with a tight enough RADAR.
ESM- Like Visual but much longer (OTH) range. Bearing data is fair to poor but contact ID is very good. "Strong" contact doesn't mean "close" but that their RADAR can pick you up.
You use these sensors alone or combined to generate an accurate TMA solution while getting an over-all picture of your tactical situation. Which sensor(s) you use depends on your tactical situation.
TMA relies on
changes to bearing rate data, its easier to track a target from the side than from dead astern. Generate a TMA solution then change course and/or speed. Note how the TMA solution falls apart (or doesn't) to make refinements to your target track.
