Suunto Compass - how to set magnetic declination
ฝัง
- เผยแพร่เมื่อ 14 พ.ค. 2023
- How to set the magnetic declination on any Suunto compass. This video shows how set a compass with a fixed declination scale and those with a semi permanent declination adjustment when taking a bearing from a map.
It was surprisingly hard to find a video explaining this. Most search results i got were how to calibrate electronic systems internal compasses.
I have a Suunto A-10 compass. I prefer to just do the math, addition in my case. So if the map shows a true bearing of 120 deg., I pick up the compass and rotate the bezel 10 more degrees (declination here in Ontario is 10 deg. west) to achieve the magnetic bearing. This is actually what you are doing by rotating the bezel using the red scale. Remember, "declination west, compass best, declination east compass least".
I also own an old Silva Ranger compass. This compass used to be used by the Canadian army back in the 1980s. It has the adjusting screw, which is simple to use. I do not think Silva compasses are as good as they were in 1980, so Suunto is the way to go now.
Careful, you’ll have to do the opposite if you’re transferring magnetic bearings onto your map.
The mnemonic that works in all cases is WAvES = West add, East subtract. The map is floppy and waves at the compass. The compass waves BACK at the map.
These days, Suunto is also not what it used to be. Owned by Chinese conglomerate Liesheng as of 2022.
I ❤your channel and how you explain the topic.
Interesting tip i never remarked it but nice to now. The fix Magn. Decl. scale on the North side of the compass, the adjustable scale a-on the South side. Maybe i have never remarked or seen this because al my compasses always had a adjustable scale.
Thank you!! You made this very easy to understand
Glad it helped!
Thank you for sharing.
I think that if one make it a rule to only use the orienting lines to align the compass with the map it will not matter if the compass is adusted for magnetic declination or not. And just use the orienting arrow for aligning the compass needle with your set bearing.
BTW. Great videos. Keep them coming
Thanks for information. I have just bought a Suunto A30. And I wonder that once I adjust once 15 degree manuel, should I use that till I use for the map. All the time I don't need to adjust 15 degree right?
With A30 (fixed scale) you should set the declination each time you change the bearing.
У вас большой опыт и отличная коллекция компасов. Вопрос, какой компас ваш любимый?
Спасибо. у меня действительно нет любимого
Pomogłeś zrozumieć to wszystko w prosty sposób dziękuję 👍
Hello and thank you very much for your lessons. I am new to your channel. Could you tell me what the little black needle on the semi-permanent declination compass is for? My Suunto compass has one and I have no idea what it is for. Many thanks
Robert
It's the clinometer.
See this video for more details: th-cam.com/video/4LR14ue0Gz8/w-d-xo.html
If I use the semi-permanent setting, and I adjust it for my area's declination, then I don't need to add/subtract when going from map to the world. Do I also no longer need to adjust when going from world back to map?
When a semipermanent compass is adjusted, how does one take a bearing from a ground feature. With the non adjustable compass you're supposed to do it backwards, right?
Semi-permanent (declination adjustable) compasses (Silva Ranger) were used by the Canadian army way back when I was an infantry soldier. I have one in my hand right now. When you are taking a bearing from a ground feature, the magnetic needle is pointing to magnetic north and the bezel scale is pointing to true north, so you do not need to take declination into account since your compass already is. That is why the army uses these compasses, so soldiers can quickly take true bearings to adjust artillery etc.
If you do not adjust the compass (ie: you only have true magnetic north to go by), do the following:
-take the bearing to the land object (the mountain summit, etc.).
-if magnetic declination is EAST, then ADD the amount to your bearing, and the sum is the bearing you use on the map. For example, if the mountain summit is at 70 degrees by compass, and magnetic declination is 15 degrees East, then you would add 70+15 and use the bearing of 85 degrees to find the location on the map.
-if your declination is WEST, you would subtract the declination amount from your compass bearing measurement, and that difference is the bearing you use on the map.
If taking a bearing on the map first, you do the opposite to find the corespondent bearing by compass. So, if east, subtract declination from map bearing. If west, add declination to map bearing.
If you adjust the compass, then you don’t do anything. Your magnetic compass corresponds to the geographic north (where Santa lives) or grid north (if you set it to grid north). Be sure you adjust the compass correctly. If you don’t know the difference, don’t adjust the compass.
I recommend not adjusting the compass until you have mastered adding or subtracting declination. It will become first nature. Once you master it, you won’t ever adjust the compass. It’s easier this way. Good luck.
Simple: Use the orienting lines only on the map and use the orienting arrow only with the needle.
I am wondering…
Given the example here with a declination of 15°W couldn’t you simply add (subtract if E) the declination to (from) the map bearing directly instead of having to readjust again?
So in the first example we get the bearing of 101° from the map and instead of going through the readjustment by using the declination scale just set the bearing to 116° since that is the result of 101° map bearing + 15°W declination (the compass itself also shows 116° after adjustment)?
Yes, you can just do the maths. But this is a YT instructional video, so I thought it was a good idea to go through the steps individually.
I hope this helps.
I assume that declination is set from grid north rather than true north, not that there's much difference between the two where I live.
For our purposes (walking / navigating with a hand held compass) it's best to use grid north as it saves a lot of time (and maths).
The difference between true and grid is caused by trying to project a 3D object on to a 2D map (That's another video I may do at some time 😀) The distances travelled, when walking, make this difference hardly worth bothering about for most people.
Obviously if traveling long distances (e.g. flying, sailing, etc.) then the difference becomes important. But I always try to keep my videos focused specifically on land nav so when out for a day's walk you can treat true and grid as the same.
I completed a coastal navigation course presented by the Canadian Yachting Association some years back. The instructor specifically told us to round all bearings for the helmsman to the nearest 5 degrees. He said the graduations on a typical boat compass and the ability of someone to actually steer a small boat better than +/- 5 degrees was problematic.@@TheMapReadingCompany
Settable declination is a great feature for those of us who are lazy. But make sure to do it right; a wrong declination adjustment can really confuse and disorient. . I did this once moving between far NE US (15 degrees W) and far NW US (15 degrees E); it took maybe an hour on the ground before the dissonance between terrain and compass bearing grew so insistent that I twigged the mistake.
User problem
When I check the magnetic declination in my area, it says '+2.97° (3°58')' so I assume that the correct declination to set is the 3°58' East? Thanks
+2 58 (maybe simpler just to set for 3 east)
May seem a stupid question, but why 2°58'? How do you work that out? Not being facetious or daft, just trying to learn. @@TheMapReadingCompany
Hi Colin, thanks for your email - sorry I missed your subsequent question. I’m going to take a guess here (which may be wrong) but a lot of these types of websites, which give the declination based on the World Magnetic Model, tend to use either the Fortran codes or they may use the Model C (World Magnetic Model C) and this gives two answer to the basically the same question - one of which will, obviously be wrong.
The way around this (two answers) is to use take the first digit of the first Fortran code result (in this case the 2) and the fractional of the second (in this case the 0.58).
It is REALLY difficult to get some website code to work out declination and it is beyond the capabilities of most individuals.
I would suggest using one of the Government or scientific body sites. For example:
USA - www.ngdc.noaa.gov/geomag/calculators/magcalc.shtml
UK - geomag.bgs.ac.uk/data_service/models_compass/gma_calc.html
I have a Suunto MC-2G. It’s not that hard to use the key. But thanks for the video!
Another question, if I may: why are there semi-permanent settings and other fixed scale compasses. Semi-permanent ones are less practical and cost more! I hope I don't bother you with my questions and thank you.
Some people only want to take a bearing from a map and follow it and a semi-permanent setting means you don’t have to keep adjusting your compass each time you take a bearing.
See this video for more details: th-cam.com/video/hjjAgPzKfG4/w-d-xo.html
OK GOOD ! THANK YOU SO MUCH@@TheMapReadingCompany
Aquí en mexico, este tipos de brújulas presentan un fallo después de comprarla aproximadamente en 3 meses se presenta una burbuja en la capsula no permitiendo el movimiento de la ajuga o impidiendo el movimiento de esta fui al servicio técnico de aquí en mexico suunto mexico la cual no se hace responsable de este fallo y te alienta que compres otra bujula de otra marca mejor. triste pero cierto no te dejes estafar por esta marca.
Mils are for winners .
Explain yourself, please. What’s better about mils with regards to declination correction?