Some mounted situations may call for you to combine and use both methods. Just remember the characteristics of each.
a. Terrain association is fast, is error-tolerant, and is best under most circumstances. It can be used day or night if you are proficient in it.
b. Dead reckoning is very accurate if you do everything correctly. You must be very precise. It is also slow, but it works on very flat terrain.
c. You frequently will combine both. You may use dead reckoning to travel across a large, flat area to a ridge, then use terrain association for the rest of the move.
d. You must be able to use both methods. You should remember that your probable errors, in order of frequency, will be—