Based on my experience, I'd say terrain association is a really important supplement to the disciplines I learned in Scouts and the Army (pace counting, walking a bearing, section ((aka triangulation)), resection, plotting azimuths and back azimuths, etc). Terrain association is the practice of connecting what's on the map with what you actually see in front of you. Terrain association is super useful if you're in an area with good visibility and distinctive terrain. In non-distinctive terrain (plains, flat dessert, etc.) or in low visibility conditions (rain, snow, heavy forest cover, etc.), terrain association is a little less useful.

HJ