Map, Compass & GPS

Map, Compass & GPS
Wild flowers along Fall Creek on the way to the Green Lakes - Oregon

Sunday, March 5, 2017

Terrain Association

“A good view will help to form a picture of the shape, the patterns and grain of the land itself.  High ground will tell a story of the geological formations and erosion.”
                                    The Natural Navigator by Tristan Gooley

Terrain association is a key step in land navigation.  While the topographic (topo) map identifies terrain features through the use of contour lines, colors and symbols, terrain association is a process of confirmation of map to land features.

In the field, the key first step in terrain association is to orient the map.  Orienting a map is a starting point to identify where I am, where I want to go and where I have been.  When oriented, map north will match geographic north on the ground. For information on how to orient a map read my supporting post.

 I orient my topo before I leave the trail head and at regular intervals during a hike.
A key component of terrain association will be the evaluation of the information provided by the contour lines.  Contour lines identify five key terrain features that include hilltops, valleys, ridges, depressions and saddles.

“Match the terrain to the map by examining terrain features.”
                                    US Army Field Manual FM 21-26 Map Reading and Land Navigation

Gain a clear view of the land in the immediate area before comparing map to ground features.  If needed get an elevated view of the surroundings.

While looking at the map, I break down the terrain and lay of the land into two components that I refer to as pathways and boundaries. 
Pathways make up my route through the backcountry.  Pathways are trails, old “jeep roads,” government roads (e.g., Forest Service and Bureau of Land Management gravel and unimproved roads.)  Not all trails and roads are pathways.  In an area lacking trails and roads, an open area clear of significant vegetation may be a pathway.  Similarly, a valley or ridgeline might be a pathway too.  Importantly, the pathway will be in the direction of desired travel.  Finally, the hiker needs to ensure the pathway is safe and he is physically up to the task. 
Trail guide books are an excellent source for finding a pathway.  Many of the newer publications offer coordinates for the GPS receiver, map views and a description of the recommended route.

Boundaries are major land features that help guide the hiker along his path too.  They are features that provide containment and may prevent the hiker from going far off track.  Boundaries can be rivers, streams, rail road beds, roads and large features such as a mountain range or ridge line.  Boundaries keep the hiker within the route of travel.  For example, if a stream is crossed then perhaps the boundary has been violated.  

Figure 1 In the image above the blue line is the pathway with the borders and boundaries in red.
In the image above the blue line mirrors an existing trail and is a pathway.  The two red lines border steep terrain and are the boundaries for this hike.

Start the terrain association process at home.  By reviewing the route on the kitchen table one begins to develop a mental map.  Maps reviewed with trail guides and conversations with those knowledgeable of the area improve the hiker’s familiarization of the backcountry pathway; this is the detail that improves and supports navigation.  The refined mental map aids in the correlation process while in the field.

Practice and frequent review makes the task of terrain association simpler over time.  Involve children in the process too.  They will be your future navigators.


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