One of the the more useful navigation tools that I had forgotten about, but was reminded of during the navigation portion of a recent course with RAT was the use of clear nav cards. They were also demoing their new Survival/Navigation Notebooks which also include one page of hard clear plastic that is printed and can be used as a non-magnetic "compass" to find your heading. The process to use these cards is simple, but when you see it work for the first time, it makes you scratch your head for a minute. Now these cards aren't a replacement for a compass. They do a fine job giving you a heading number, but a compass is still needed to turn that number into a path for your feet to follow.
To illustrate their handiness, on the map above a path has been marked between Hanging Mountain and Sugar Hill Pond. Knowing the area, I could guess that the heading should be a bit west of due north, but that's about as specific as I could tell you offhand. Using a map and compass, the first task would be to spread out the map, align the edge of my compass to a north/south indicator like the map border or grid line on the map, and then orient the map itself so that north on the map points north in real life. Once I have done that, my compass, map, and the real world all line up with each other (except for declination which I pretend doesn't exist most of the time!).
With map aligned, I can move the compass back over to the path I have marked, align the edge of the compass with the drawn path, and then rotate the compass bezel until north on the compass bezel lines up with the red magnetic indicator. At this point, it is apparent that my direction of travel will be right around 332 degrees. Not quite north, but certainly northward and this would seem believably close when I line it up against my knowledge of the area. I expect this is how most people who use a map and compass work the two together - lay the map down, orient the map, align the compass to the path, box the arrow, and then read your heading. Pretty traditional stuff.
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Now, let's screw up the orientation of the map
so that north on the map is pointing eastward in real life. |
If you do navigate using this method above, you know how hard it is to maintain the map's north/north orientation, especially on uneven ground or on a boat or even on a windy day. Here's where those clear cards come in handy! The whole reason you have to orient the map is because your compass needle is always going to swing north, and there is nothing you can do about that. But with the cards, the north mark points whichever way you want it to. Since north is clearly marked on every topo map, you already know in the map's world which way north is. To find your direction of travel, you just lay the clear card on a north/south line on the map, line up the 360 and 180 marks on the card with that line, and your card and map are now aligned, even if you are facing west or even holding the map in your hands. Center the dot on the card over your marked path and your heading is apparent - very close to 332 degrees. No worrying about having bumped the map or finding a flat surface to lay it on. Just slap the card down, align the directions with what's marked on your map, put the center dot over your path, and read your heading! Of course, you still need the compass for when you start moving unless there are some unmistakable visible landmarks you can use.
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