In the LKP scenario, what is the recommended positional uncertainty radius error (X-Error) for a GPS position?

• A. 0.5 NM
• B. 2.0 NM
• C. 1.0 NM
• D. 5.0 NM

Answer: (C)

The main idea here is understanding what X-Error represents in a GPS fix during a Last Known Position (LKP) search. X-Error is the radius around the reported GPS position within which the true location could lie, taking into account the horizontal uncertainty of the GPS system and any small movements since the last known fix.

In an LKP scenario you want a practical bound that captures the real possibility area without turning the search into a sprawling, inefficient effort. A moderate radius is the best fit because it acknowledges that GPS positions aren’t perfect and that the subject might have drifted a bit since the last contact. If the bound is too small, you risk missing the target due to underestimating the GPS error or unaccounted movement. If the bound is too large, you waste resources by searching areas unlikely to contain the subject. The moderate X-Error strikes a balance, providing a sensible, efficient search area that aligns with typical SAR planning practices for LKP scenarios.