Just to give an example using the wonderful resources available on PG-HQ. Map 22 can be seen at the URL located at the end of my post.
Assume there is an unspotted enemy unit in hex 1216 and that it is daytime.
Case 1. A unit in hex 1213 can spot it because 1) the hex it is within 3 hexes of the limiting terrain in 1216 (8.21), and 2) the LOS only crosses one light woods hex (the one in 1215)/
Case 2. A unit in hex 1212 cannot spot it because it is further than 3 hexes away from the limiting terrain n 1216.
Case 3. A unit in hex 0915 cannot spot it because although it is within 3 hexes of the limiting terrain, its LOS is traced though two light woods hexes (1015, 1116) and thus it is blocked as per the Light Woods note in the Terrain Effect Chart.
If the enemy unit in 1216 had a Spotted marker on it, then the unit in Case 2 above could spot it because it would be within normal spotting range (12 hexes). The unit in Case 3 would still unable to see it because tracing the LOS through to Light woods hexes blocks LOS.
Hope this helps!
http://www.pg-hq.com/library.php?type=map&id=22
