In FotRSU, you can generally use the green circle as your compass-drawn territory limit designator. ie: stay inside the green circle and you are within the boundaries of the patrol zone. Most are highly accurate. Some are rather loose, so stay away from the immediate are of the "edge" of the circle. With the "Sink" missions, where you are told to proceed immediately to a certain location, and once you are in the area, you receive a message to Sink Enemy Shipping, that can be done anywhere on the NavMap that you can find enemy shipping to sink. You will generally not see a green circle in those cases. If you have a SpecOps mission and you have a green circle, those are generally much smaller, on the order of maybe a couple-three nm across, which is the active area for the SpecOp. Not all SpecOps will have a green circle though, in which case you try to get as close to the "Star" as you dare, in order to perform the assignment. You might also be assigned one of those in conjunction with a "Patrol" objective that has its own larger green circle, and you might also encounter missions with "hidden" objectives that are revealed as you progress through the first objective assigned. Generally speaking though, if you see a green circle, that is your assigned area of operations for the given task and / or time frame.
