After reorganizing my get home bag I decided to compare the protractor compass I keep in there to the little one on the side of my emergency whistle. They were a few degrees off from each other while pointing north. I took out a lensatic compass and another protractor style and was surprised at how different they all were (by about 2 degrees).





How do I determine which one is correctly pointing north?





Before anyone mentions it, I made sure each compass was not close enough to the other to eliminate magnetic influence on the pointers.





These are the types of compasses I was comparing (taken from the web).










 

Well since nobody brought this up, I will.  

Magnetic north is not true north.  In fact, its a fixed point so a compass will be off depending on where it was calibrated compared to where you are.  Any compass, you need to compare it and with better compass calibrate it to true north.  Everyone of those compass if consistent works.  Unless one was made where you live, its probably not pointing to true north.  

What I'm getting at here is you don't really have to have it pointing at true north as long as you know the difference.  What's important is it points the same direction every time.  

What we do with real compass is we use a GPS then calibrate our compass depending on where we are.  Otherwise, its not a big deal but a matter of addition or subtraction.  

Tj Story Time  "Navigating with no landmarks at all not even the sun."

During the 1970s and 1980s, I was canoeing fool. Living in E. TX, I was determined to navigate every body of water on the Gulf Coast west of the Mississippi.  I made a pretty good dent in it over the years, but we didn't have tools like a GPS in those days and really a compass isn't much good going down a river, you are pretty much going where the river takes you.  One long weekend, my canoe pal Doug and I decided to do the  Atchafalaya basin.  Holy cow did our world just change.  Warm weather and wet season, its like an ocean.  You can move in any direction you nose your boat.  Worse, its like an ocean with no sky because the trees hid the sky.  There was no hills to navigate by and due to shallows, you cant' really strike a straight line.  

Other than the levy to the east and to the west and miles between the two, there's really only one landmark and its a good one.  Like a river in most placed, it has I10 that goes east and west across its north center.  You couldn't miss it and as long as you knew if you were north or or south of, you had a way to navigate.

Going in, it didn't take long back then to realize, we'd just entered a New World.  It was so isolated back then, it truly did have its own culture and like a science fiction book a hidden world.  There were people in there that didn't speak a word of English.  Many lived on floating boat houses and many lived on high spots.  I'm talking so rural the traditional house on stilts with pirogue (pronounce pero) was like the big city.  The wildlife was like out of and Edgar Rice Burroughs novel and everything wanted to eat you from the bushes full of cotton mouths to the wild hogs (I'm not talking game hogs here but once ancestors were domestic monsters).  If a Banana spider wasn't jumping in your boat a gator was trying to mate with it by coming up underneath it trying to lift you out of the water.  The mosquitoes were so thick we told each other they flew in "V" formation and wouldn't stop till they got a pint.  Like the bad move from that era about an Army platoon lost in there, this was not a place you wanted to be lost in, but it was a place you were lost minutes after you put in.  

(BTW, Unlike the movie, the people in those swamps were simply fantastic folks, friendly, easy to meet, and tried to feed you.)  

You can't really sleep in canoes especially knowing falling in may be the death of you.  We spent much of our evenings looking for dray spots suitable for camp and would camp early rather than bypass a good spot.  When it was time to find our truck, I had a cheap liquid filled compass I picked up at an autoparts store in my tackle box.  We made our way north to the interstate then west to the Levi.  

Tj

No its not and we don't really care that  you have some non-contributing smart comment either.

Tj

LOL, No, my GTT score was high enough I didn't have to settle for a 11B.

Marine and vehicle compass have a calibration feature for the specific vehicle/magnetic interferences and subsequently what area of the world you are in.  In handhelds, you orientate the compass to true north, in other words compensate for magnetic north versus true north, some you have to do the math, some you simply move the compass, some you move a dial.  You calibrate it to true north.  

Here's a little write up on how to.  True North Versus Magnetic

Now any compass as long as its consistent, always points the same direction, you can calibrate it by knowing what the difference is from where it points consistently to true north.   In general, the only bad compass is one that's not consistent.  It can point East and long as it does every time, then you can navigate by it.  Trusting that a company does this for you, not good, because compass are not all made in the same part of the world.  There's really three points, true north on most common maps, magnetic north, and magnetic bearing where your compass points to.  

I navigate by compass about six months a year and have for over 20 years and not just here to the next hill but miles upon miles. My boat compass is calibrated to true north which matches my Army Crop of Engineer charts.

Tj