Friday, September 24, 2010

Topo Maps and Profiles

Navigating and understanding land forms and profiles is a skill I'm working on this winter. Years ago I obtained this Forest Service Map of a local section of national forest which is very diverse in rivers, gorges, saddles, cliffs and waterfalls. The photo below is of a profile I've done to compare visual concepts mathematical tools.

Depending on the graphing gradients used, a trail can appear either quite difficult (the yellow line) medium in difficulty (green line) or fairly benign (red line). I really noticed this discrepancy in perception while hiking the Appalachian Trail. Most data was presented with the same markers and gradients until we reached Maine. Then, the profile seemed to be so horrendous, appearing as though it were impossible. With more careful study, one could see the miles were placed close together, while the elevations were space out on the vertical graph. Thus, to climb 400 feet in one mile appeared daunting. Had the miles been spaced further apart on the horizontal line, the climb would appear less formidable.

Lesson: always find the map key for numbers critical to the true picture.

This topo map has the contour lines marking at 20 foot intervals. Each dark line represents 100 feet. The closer they are together, the steeper the slope. But, because each block represents a square mile, one can see that the area has many gorges and slopes in a given mile. A map of Kansas, for instance would show very few contour lines.

I've found some trails and old logging roads in the area that are not recorded on this map. I have begun to pencil them in. A compass is essential in this work to keep it real. Also, some trails shown on the map have ceased to exist due to abandonment.

Some trails have an occasional hunter or horseback rider. For the most part, there have been no signs of motorized vehicles. No trail sign has been found indicating wheels of any sort.
These skills are useful if a person gets disoriented in the back country. Finding the way down stream to larger streams, learning to hike a straight line in a challenging terrain (keeping the sun at one's right shoulder for instance) is very interesting.
I always bring a compass, knife, flint, and large plastic bag in my pack just in case.

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