Use Lensatic Military Compass

WolfBrother

Member
https://knowpreparesurvive.com/survival/use-lensatic-military-compass/


A good start - it does mention declination.

With the movement of the magnetic North Pole, the North your compass pointed towards 10 years ago has moved enough that old maps declination are off.

I moved to Austin, TX in 1985 and bought some Topo maps of the area (Pedernales falls, Enchanted rock among them). Most of them had pre-1985 dates on them.

Based on this Declination calculator https://www.ngdc.noaa.gov/geomag/calculators/magcalc.shtml#declination on January First 1985 the declination for Austin, TX was:
1985-01-01 7° 5' E changing by 0° 5' W per year.
Now it's:
2019-01-01 3° 42' E changing by 0° 7' W per year
In the past 34 years the declination has changed by a total of 3 degrees and 17 minutes. or 3.283 degrees.

I calculated that a degree off at one mile is 92+ feet. SO today hiking a mile on a correct declination map for 1985 you will be off by 302+ feet. In football terms - you intercept a pass 2 feet into your endzone, you have to run 302 feet to score a touchdown.

ALL of my maps are updated yearly as to correct declination.
Any trip I go on, I take a list of cities and their current declination.

I use the ngdc.gov site above for that.
 

Atlas

Administrator
Staff member
Very good point. Chart corrections are a very important part of navigation, ask any sailor!

More importantly, are we all practicing with map and compass? Living in the city is not an excuse!
 
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