Part of the Ottawa Rambling Club's leader training program is provisioning members with the skills they need to competently navigate off-trail. While working with a couple doing just that as they prepare for an upcoming Long Range Traverse, we practised the two main techniques in getting from point A to destination B in unfamiliar territory using just a topo map and compass.
Either you head to B 'on bearing' making a straight line for it, or, you 'handrail' an appropriate linear feature such as a river or a ridge you see on the map, following it like a handrail to the destination. In the example below, taking the red arrowed direct approach, following your compass carefully, is much shorter than than handrailing the streams and ponds. However it also means having to climb steeply (where the contours bunch) then descend towards the destination. The green arrowed handrail route on the other hand is almost level.
Both techniques demand that you are capable of associating the map's topographic features with those terrain objects you eyeball in the landscape as you pass by, through or over them. The chief difference between the two methods is hiking direct bearings demand accurately following your compass whereas handrailing requires only keeping track of an approximate bearing. Deciding which one to use is entirely based on the experience of the leader, who must consider both human factors such as participant fitness levels, as well as geographic considerations such as time of day and terrain conditions.
Frequently the choice is made easy. For instance, the map below shows a trail-accessible pond that is close to an off-trail mountain spur with a fine view. Since there is no obvious handrail and the slope is only moderate, measuring a direct bearing to B from the map, then using the compass carefully in hiking a tight line is the way to go.
When is handrailing an obvious choice? Check this out. At the end of an access road, point A, a hike leader wishes to get to a wonderful lookout at B. Perusing the topo shows that a long, well defined ridge runs between the two. The group gets there by staying on top of the ridge as it rises to B, roughly tracking north-northeast. Note the steep downslopes on either side of the route. Any significant descent along the way would mean the leader is off-route. At that time a correction would be made by heading up-slope to gain the ridge's high ground once again.