Yet another way to navigate across a mountainous terrain is by using a compass or altimeter. One can correlate his position with respect to specific landmarks in the surrounding terrain to identify your approximate location on a topographic map. This usually happens using the intersection of two reference lines:
Ridgeline and altitude (altimeter)
Ridgeline and bearing (compass)
Altitude and bearing (altimeter, compass)
Two bearings (compass)
Let’s take a closer look at each scenario in detail.
First option – Ridgeline and altitude. Say we are walking along a ridgeline (line 1). We have an altimeter watch or barometer that tell us we are at 2050m altitude (line 2). Our current location is identified by the intersection of the ridgeline and 2050m contour line as shown below.
Option 2
Let’s say once again we are climbing up along a ridgeline (line 1). We now take our compass and identify a prominent peak at 300 degrees Northwest (line 2). Once again intersecting both lines – bearing and ridgeline identifies our current position.
Option 3
This time we are off the ridgeline. We are now following a trail at 2000m altitude (line 1) as per our altimeter watch. We again take a bearing towards a prominent peak on the Northwest – 314 degrees (line 2). Intersection of the bearing and contour determines our approximate location.
Option 4
Final option would be to locate two prominent landmarks in the landscape (peak, tower, saddle…) and take two bearings with compass. Intersection of both bearings identifies your location as shown in below illustration.
One important info – use reference lines (bearings, contour, ridgeline) which intersect nearer to a straight angle (90 deg) for best accuracy. Avoid intersections at very narrow (0 deg) or wide (180 deg) angles which will introduce larger errors / less accuracy in determining your location.
Assignment
You are hiking in the lower Dhauladar in the region Northwest of Dharamsala:
https://www.openstreetmap.org/#map=13/32.3552/76.2308&layers=C
Use the 4 methods above to identify your location on the map using 2 reference lines. Submit 4 maps with notes in a public folder for review. Use (parts of) this compass image to measure bearings on your map:
https://drive.google.com/file/d/1IOddTl-t1KLw82ojoBH4llVZHnXOlQln/view?usp=sharing
