Terrestrial reconnaissance, or ground recon, is a type of reconnaissance

Reconnaissance

Reconnaissance is the military term for exploring beyond the area occupied by friendly forces to gain information about enemy forces or features of the environment....

 that is employed along the elements of ground warfare

Ground warfare

Ground warfare or land warfare is the process of military operations eventuating in combat that take place predominantly on the land surface of the planet....

. It is the collection of intelligence

Intelligence collection management

Intelligence Collection Management is the process of managing and organizing the collection of intelligence information from various sources. The collection department of an intelligence organization may attempt basic validation of that which it collects, but is not intended to analyze its...

 that strictly involves routes, areas, zones (terrain-oriented); and the enemy (force-oriented). Ground reconnaissance is considered to be the most effective type of reconnaissance but also the slowest method in obtaining information about the terrain and enemy.

Those units in contact with the enemy, especially patrols, are among the most reliable sources of information. Combat engineers are also good sources of information. These engineer units often conduct engineer reconnaissance

Engineer reconnaissance

Engineer reconnaissance is the reconnaissance operations performed by combat engineers to enable forward movement of own troops, in war usually over territory previously occupied by the enemy...

of an area and can provide detailed reporting on lines of communications; i.e., roads, rivers, railroad lines, bridges, and obstacles to maneuver.