Friday, August 9, 2013

Land Nav - Baseplate Style or Lensatic Compass?

Photo: my Cammenga 3H w/ Ranger Bead Neck Lanyard
 I love land navigation with map and compass! If you've been following me for a while, or have read the forward to the new J.D. Lenzen Book, Paracord Fusion Ties Vol. II, you'll know that one of my first paracord creations was the all-paracord army ranger pace counter beads. With the advent of GPS and smartphones, many people ignore learning traditional land nav skills - to their own peril. I wanted to learn these skills and found the wealth of technical information I was looking for at Michael Neiger's website. Michael is the lead investigator for the Michigan Backcountry Search and Rescue (MiBSAR) and adopted my all-paracord bead, indicating that they are the best he's ever used.  http://therucksack.tripod.com/landnav.htm#pacecounting

The necessary companion to ranger beads is a quality magnetic compass. AVOID relying on digital compasses and phone compasses except as a last resort  (just grab one and compare the results to a magnetic compass if you don't believe me). I have amassed quite a collection of compasses over the years, some cheap and some quite expensive. They have all been baseplate, button or ball style. Recently I acquired my first lensatic compass and its a badass piece of gear! The model 3H Tritium Compass is pure landnav awesomeness.

"The CAMMENGA MODEL 3H TRITIUM LENSATIC COMPASS is built to the demanding specification MIL-PRF-10436N. Battle tested through rigorous shock, water, sand proof, and functional from -50o F to +150o F. Seven Tritium Micro Lights allow for navigation in low-light conditions, without the need for a flashlight or any other light source. Tritium Micro Lights remain luminous for over twelve years, maintenance-free. Equipped with a magnifying lens, sight wire, and dial graduations in both degrees and mils to ensure accurate readings. The Copper Induction Damping System slow the rotation of the magnet without the use of liquids. Built to last with an aluminum frame and waterproof housing. The CAMMENGA COMPASS is depended on by fighting forces, government agencies, and adventurous outdoor enthusiasts around the world."

This Cammenga compass is "bullet proof". The solid construction is noticeable the moment you handle it. The compass employs an induction dampening system (magnetic forces are used to settle the spinning needle). This is a very welcomed feature for me. All my liquid filled compasses have bubbles. One of my most expensive compasses is the Brunton 8099 eclipse pro. Its liquid dampened and inevitably develops a bubble that grows and grows. They always say a small bubble is of no concern, but who wants to think about that?

I've found lensatic compass use simpler in some ways and more complex in others. Want a simple simple bearing of which direction your facing? You need to point a baseplate compass direction of travel line ahead and turn the compass housing to align the north arrow with the designated marker on the dial; then read the bearing. On the lensatic just point and read. 

How about orienting the map? I'll give the lensatic a slight edge because there is no need to set a zero bearing on the compass housing first as with the baseplate compass.

As far as sighting a bearing or a landmark to walk to or triangulate your position; you simply can't compare the accuracy of the lensatic's magnifying lens and wire sighting system to the approximate result obtained from a typical baseplate compass pointing approach. It should be noted that there are more costly baseplate compasses with sighting systems, including mirror style versions that can serve secondary function as a signal mirror. As long as we are citing multiple use features, the lensatic's magnifying glass can be used with the sun to start an emergency fire under the appropriate conditions. 

The process of transferring field (magnetic) bearings to map (grid) or vice versa is similar with most baseplate and lensatic models. The navigator must add or subtract the declination value PROPERLY to convert between mag and grid. This can be the most confusing aspect of landnav to the beginner, especially if not explained well. Here Is where some of the more expensive baseplate compasses shine - they may be equipped with a declination adjustment screw. A simple adjustment to the map declination before hitting the bush allows the user to compare field (magnetic) bearings to map (grid) bearings mindlessly (no math). Personally in prefer to do nothing mindlessly - what if you forget to adjust to a new location; or if something caused the adjustment to go out of whack, however unlikely?

For me, the simplicity, durability, sighting accuracy and induction dampening are enough to make this my new compass of choice. However there may seem to be a VERY good reason to use a baseplate compass over a lensatic: the baseplate compass serves the function of a protractor. 

When using a lensatic compass, you need a separate protractor for transferring bearings to a map, or taking a map bearing before setting your compass direction in the field. Technically u can get away without a protractor by orienting the map first, however I believe that there is a practical matter with doing this on uneven ground, and maintaining the map orientation hinders accuracy.

Whether you have a baseplate or lensatic, you'll need a grid overlay to accurately plot your location on a map based on GPS coordinates; or to pull coordinates of a feature to manually set a waypoint or to relay information to SAR. It is foolhardy to rely solely on the phone or GPS built in maps. TIP: The Trimble outdoors navigator pro app will still give accurate GPS coordinates using true iPhone's GPS EVEN I'VE THERE IS NO CELL SIGNAL. 

You also need a scale with gradations to match the map scale to correctly measure map distances. Compass baseplates usually have one or two common scales but they won't do you any good if your map is a different scale. These baseplate scales are pretty short, making it difficult to measure a distance or set the bearing when the target point on the map is further away than the length of the baseplate. 

The good news is that you can buy a quality coordinate plotting tool that includes multiple map scales AND a protractor (such as the one I picked up at maptools.com).  The item has a small hole in the center to which you can fasten a one foot piece of paracord inner strand. This effectively allows you to stretch and measure a bearing between any two points in the map. Using this tool negates the baseplate compass "protractor" advantage. 

In conclusion, there are many reasons why some people prefer baseplate compasses and some prefer lensatic style. It's worth noting that the United Stated military forces train with and use the Cammenga lensatic model. I hope the information I've provided gets you thinking enough to make an informed decision about which is best for you. Whatever you choose, don't buy a cheap piece of garbage from the Walmart camping aisle. Buy a compass like your life depends on it - because it does. 

Written by Kevin Gagne

4 comments:

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  2. To each his own, but I really prefer the conventional compass wherever I go. Simplicity is beauty and for me, I want a compass being compass and being reliable whenever I feel lost or I need an update in the direction where I am heading. Christmas is around the corner, and a compass is a great gift idea if you’ll ask me. Check the best compass options here: http://backpackingmastery.com/top-picks/the-best-compass.html

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