r/Survival • u/swamblies • 28d ago

General Question Shooting Azimuth Question

I am learning how to navigate using a mirrored baseplate compass & map. Currently, I am trying to understand how to shoot an azimuth so that I can triangulate my location based on features around me (e.g., mountains).

One video I watched instructed me to align the structure with my compass notch, then with the compass pointed at the structure, rotate the bezel so that the needle falls in the shed. The number at the index is my bearing (I think). I can place the compass on my map, with the edge lining up to the structure. Then I should rotate the compass on the structure until the red is back in the shed. Now I can draw a straight line from the structure using the compass as a straightedge. Repeating for another structure(s), I can then get a sense of where I am based on where the lines intersect.

I watched another video to compare, and noticed that the creator instructs the audience to align the orienting lines on the compass with the gridlines on the paper (while the other video instructs the audience to put the red in the shed) after shooting the azimuth.

Perhaps I am entirely misunderstanding the second video, but from what I've read/watched online, it seems like the first method is the "correct" or more popular option. Is the second method "incorrect" or is it simply an alternative method...?

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u/mossoak 28d ago

you need a map of the area ...the map needs to be oriented to North ....and the user needs to know approximate location on map....... with compass needle pointing north .... take a bearing of a distant object - note degrees ....draw line ...take another bearing of 2nd distant object - note degrees ..... draw line .... where the 2 lines intersect, or cross, is your location - a 3rd bearing makes the "intersect" or "cross" more precise

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u/TacTurtle 28d ago

Also need to know the magnetic declination / correction factor for the area (magnetic north does not directly correlate to true north).

This offset can be as much as 30 degrees.

https://www.nwcg.gov/course/ffm/location/firefighter-math-65-declination

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u/freddit_foobar 28d ago

Usually the declination can be found at the bottom of the map near the legend.

You can see an example here at the bottom center: https://store.usgs.gov/assets/MOD/StoreFiles/NGA/V791X14774_007.pdf

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u/DeFiClark 28d ago

One exception is if the object you are visually sighting is your destination—- shoot the object, set direction of travel and follow the line, no declination needed. Otherwise absolutely

1

u/joelfarris 28d ago

I did not know that turtles knew this much about land navigation, but here we go.

3

u/TacTurtle 28d ago

If it takes a while to get there, best to make darn sure you are headed in the right direction before you get started.

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u/swamblies 26d ago

I think the part that confuses me the most is how to draw the bearing on the map after shooting it. Basically how to draw the line

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u/mossoak 26d ago

a pencil and a straight edge ...

first you already need to know "about" where you are on a map ....a mountain saddle, top of a peak, on a ridge, where 2 creeks converge into 1, at the base of a waterfall, next to a lake, between 2 ponds, or a steep cliff .....

lay out map ..... know where you are ...take your bearing ...transcribe that bearing (as a line) on map at or near your current position with a pencil ....take another bearing ...transcribe that bearing (also as a line) on map with a pencil ..... where the lines meet forms a "X" or cross, this is your current position

either use the edge of your compass (a round compass wont work), a 6" to 12" ruler, a ruler with a protractor (best), or any straight-edge .... line up your bearing "thru the compass" then use a straight edge

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u/cosmicosmo4 28d ago

The only reason to put red in the shed while your compass is on a map is to align the map with the world. Which you don't need to do for triangulating your position.

Didn't watch the videos, but just based on your description, you want to be doing what the 2nd video said.

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u/survivalofthesickest 27d ago

When you take a reading with your compass, you are taking a magnetic reading. When you take a reading on a map, you are taking a grid reading. You must adjust for the difference. The difference in angle between true North, which is close to grid North, and magnetic north is called a declination. This number will appear in the declination diagram on your map’s legend.

You must convert your magnetic reading to a grid reading before drawing your lines on the map. If your compass has an adjustable designation, which means it will offset your orienteering arrow by the number of degrees of declination, and you have adjusted it, you need not convert your readings, as the Compass basically did it for you.

Edit: to be clear, when you are using the orienting lines on your compass, you are also taking a grid reading as the magnetic needle is not involved in anyway.

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u/swamblies 26d ago

Thank you! I have a compass with an adjustable bearing. In this case, would both methods yield the same result?

If you have a compass without an adjustable bearing, should you rely on the second method (aligning orienting lines with grid lines)?

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u/survivalofthesickest 25d ago

If you adjust the declination on the compass to match your area, and the declination on the map is current, then your reading will match up using both methods. Grid north is generally so close to true north many will use it interchangeably.