Which of the following is NOT a method of reconnaissance?

The choice indicating that signaling recon is NOT a method of reconnaissance is accurate because it does not represent a traditional or widely recognized method of gathering information on the battlefield. Reconnaissance is primarily concerned with obtaining essential data regarding the enemy's positions, terrain, and environments through a variety of established techniques.

Map reconnaissance involves analyzing terrain and enemy positions through the use of maps, which provides crucial insights for planning and executing operations. Ground reconnaissance entails physically moving through an area to gather firsthand information, allowing for a direct assessment of enemy forces and terrain features.

Air reconnaissance employs aerial surveillance techniques to monitor and gather intelligence over a larger area, offering a broad perspective that ground methods may not capture. This comprises using various aircraft or drones to assess the environment and any potential threats from above.

In contrast, signaling recon, while it may refer to some form of communication or signaling techniques within a unit to convey information, is not a structured reconnaissance method used to gather intelligence about the enemy or terrain. Hence, it is correctly identified as the choice that does not belong in the listed methods of reconnaissance.