Map, Compass & GPS

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

Tuesday, November 18, 2014

Navigating At Night In The Backcountry

This is a rather technical  overview of navigating at night.  Proper preparation is essential.

Navigation during periods of exceptional darkness and reduced visibility is a serious issue for the hiker.

Important navigation features (e.g., mountains, roads, forest, etc.) can be nearly impossible to see.  The impact is a significant loss of geographic reference used for daytime travel.  Geographic reference validates the hiker’s map.

Further compounding the nighttime challenge is the physiology of the eye. Our eyes are designed to provide optimal performance during periods of light.  The components of the eye (the retina, rods and cones) are arranged specific to their function.  The cones are the discriminators of fine detail and color.  Cones are the most effective in light. In complete darkness, a cones’ effectiveness is significantly reduced.  Rods are important to our night time vision.

What that translates to is this:  in periods of extreme darkness, the ability to see with clarity straight ahead is significantly diminished. If you absolutely must continue traveling at night, the hiker should first make an effort to become adapted to the night environment.  Avoid looking at any white light. Select a member of your group to follow behind you with the GPS and flashlight/headlamp, as its light will negatively impact your vision.

Red light is now best.  Allow 15-30 minutes for the eyes to become adjusted; older hikers may need almost one hour.  Continue to protect the now adapted eyes from sources of bright illumination; discuss this with the other members of the group before embarking.
To maximize clarity, the lead hiker will need to scan the surroundings (by turning their head side to side) rather than looking directly at objects.  This is where prior map study, commonly known as having a “mental map” will pay off significantly.

Navigation procedures are essentially the same as during daylight.  Global Positioning Systems (GPS) lose no capability and will continue to direct the hikers as before.  Do note that the display screens backlight capability do not have red lighting, only white, and use will quickly degrade battery life.  Always carry spare batteries.

Without a GPS, the navigator has the option of navigating by a process known as dead reckoning.   Dead reckoning is the careful application of map and compass by evaluating azimuths and distance by pacing.

Navigating at night is challenging, potentially dangerous, and requires a high level of knowledge.  Confidence from lots of practice performing these skills is essential.   Practicing at night is strongly recommended before heading out to the wilderness.  

No comments:

Post a Comment