Unknown contact question

[pepolk0001]

I am wondering what this yellow arc section outline is, I know it has something to do with the unknown mobile contact represented by the question mark icon.

[RoryAndersonCDT]

That represents your aircraft 'hearing' the radar emissions of a mobile ADA unit of some sort. They know its bearing to a few degrees, but don't know its distance. Thus you get a 'radial' uncertainty area.

[MrLink]

Its exactly like Baloogan says. It basically means that the question mark icon could potentially be anywhere in the area inside that box and not necessarily where it is shown on the map in your screenshot.

This usually happens if your units first detect the contact with a passive system (like your plane's RWR in this case). As time goes by the box will become smaller and smaller until you get a more exact location especially if you engage an active sensor like radar. It is important to consider the situation carefully when you have a box like that as it not only means that the threat could potentially be closer or farther away than what your units think, but also most weapons you could use would only tolerate very little (if at all) 'ambiguity' value for the target location in order to allow for a successful engagement.

[RoryAndersonCDT]

You can be clever about it too! Have two really good RWRs try to triangulate locations of radars passively. Eg, if you have two F-22s kicking around a hostile airspace, split them up, put 20nm-50nm between the two Raptors and watch as your pilots triangulate the locations of hostiles!

[pepolk0001]

Oh neat. So it's really an error ellipse (but square shaped).