What does the shaded area of some R21 range rings mean?

• A. This area indicates a previously searched zone.
• B. A Line of Bearing in that area may need more error.
• C. The transmitter is likely located there.
• D. Data in this area is unreliable.

Answer: (B)

Shaded sectors on R21 range rings flag increased uncertainty in bearings within that area. When you’re using lines of bearing to locate a transmitter or target, you rely on precise angles, but the shaded region tells you the angular error is larger there. That means any line of bearing passing through that zone should be treated with a bigger error margin, and you should supplement it with additional bearings or widen the potential intersection area to maintain accuracy. It isn’t saying the area was already searched, nor that the transmitter is specifically there, nor that all data in that area are unreliable. It’s a cue to expect more bearing error in that sector and plan accordingly.