Map & Compass 201: Declination
HTML-код
- Опубликовано: 9 сен 2024
- Let's discuss declination. Remember: Declination East: Compass Least. Declination West: Compass Best. I will discuss this principle and how to put it to use to help you become more accurate and more successful using your map and compass. This is a continuation of Map & Compass 101. For your local declination:www.ngdc.noaa.gov/geomagmodels/struts/calcDeclination
This helped improve my understanding immensely. PackRat, thank you very much.
Thanks! I appreciate you having taken the time to explain these principles. Many consider it too basic, and don't realize that not everyone has had the training or life experience to prepare them for accurate orienteering.
But for beginners that may be too difficult & confusing- I feel this may be the best video that laid it out in a simple "working" way.
AWESOME. You have the talent & patience to teach others and that is a God given gift for sure. Thanks for the layman's terms and explanations. Really great.
I have watched a few videos (first timer to using a compass and map), and so far yours gives the best technical info for a beginner. Thanks for the NOAA link. Good job!! Thanks much.
If you like to use an acronym to remember magnetic declination adjustment. You might like one I dreamed up. WAvES. West Add v East Subtract. You might remember " Map WAvES at the Compass". Because, for example, going from a Map bearing to the Compass bearing - If your declination is 8˚ W you will add 8˚ to the bearing to be set on the compass. (But if you are taking a compass bearing back to the map , you will do the opposite and subtract the 8˚ from the compass bearing)
Another way to think about it is to think of the compass rose realize that the shortest way to go from North to East is to go CW, the fastest way to go from North to West is to go CCW. And that is the same direction you would turn the compass bezel to adjust for magnetic declination. If your mag declination is 10˚ E turn the compass bezel CW by 10˚. Or for 10˚W mag declination, turn the bezel CCW by 10˚,
How far off base can you be if you don't adjust for mag declination? :
A note to bring home why you need to adjust for declination. If your bearing is off by 1˚ after 1 mile you could miss your destination by 92 ft = 30.72 yards = 28 meters. Not to bad. You probably should assume you can't walk a set bearing within a 3˚ error. Or 246 feet off at the end of one mile.
If you don't account for the 10˚ of magnetic declination, as in your example, at the end of 1 mile you could be off course by 10 x the 1˚ error. Or at the end of 1 mile if your bearing is off 10˚ you will be off course by close to 920 ft = 306 yards = 282 meters.
Knowing this should help you understand
1) why you need to set your bearing accurately and account for magnetic declination ( especially if it is > 3˚) and
2) you can never walk your bearing completely accurately and that is why the technique of Aiming Off is used. That is deliberately setting your bearing off a few degrees to one side of your destination so that after you have walked the needed distance you will know which direction to turn to hit your intended destination if it is not in sight.
FYI - How the error is calculated, if you like to think about such things.
The distance off course by X ˚ at the end of a chosen distance
= tan X˚ ( distance to destination)
Example if your bearing is off by 5˚ at the end of 1 km = tan 5˚ ( 1,000 meters)
= .0875 (1,000 meters) = 87.5 meters = 287 feet = 95.7 yards. This would be the theoretical distance off error.
I have heard about declination but never understood or knew what it's purpose was in mapping. Your video made it simple and clear. Now I have to go watch the first part! :-)
Great video Packrat, clear and precise. Thanks from the UK.
Thanks PackRat! This cleared up the confusion I was having with declination!
Probably the best declination explanation that I've found to date. Thanks for posting. Just to further confuse things, there is generally an annual increase listed on the topo map beneath the declination value. This value will help you calculate the annual change to the declination value as the magnetic field shifts over time. It looked like your map read '1983', so the annual declination change could be significant for your area by now...
Rat, I know this is an old vid, but I have to tell you, you've done a very good "Laymans" way of explaining declination. Keep your videos coming. I like the way to simplify things.
Awesome video, by far the best one I've seen so far. Thanks!!!
just learning how to use a compass/map and this video has helped me understand it alot better now Thank You and 5 stars .
That was as simple as it gets. Thanks for the video.
Actually, navigation can be a lot simpler than this. Just get a good quality compass with adjustable declination, set it correctly for your area, and then measure all bearings to true north with none of the confusing backcountry arithmetic. A great compass is the Suunto M3, get it on Amazon for about $29.
@ChristianBackpackers That's true. My Silva 515 has just this type of adjustment and I really like that. It is good to understand the basics though, just in case you find yourself using a more simple model or backup compass. Thanks for watching and commenting!
I'm gonna have to watch this one a few more times, but thanks for all of the great information!
If you factor in your declination when you orient your map, you will not have to worry about it any more. Save you a bunch of time and headache. The army does it the way you explained it
Excellent job. You sir are a great educator. Thanks!
@05MagnumSXT Thanks! I hope it will be helpful to those who are new to this. I appreciate you watching and commenting always!
Thanks so much. I really appreciate your time and effort. a=Happy trails . . . or off-trails!
Great addendum to your compass vid! Thanks!
Great Video, now I anderstant how to use declination. good work. Thank you merci
@PackRat556
Very clear and easy to understand video tutorial. Brilliant Job! Thanks for your efforts!
Thank you for making it simple! Also learned from the 101 video. Great videos.
Very nice. one of the best intro s I have seen..
@veritasfiles Your welcome. I hope it is helpful for you. Thanks for watching and commenting!
Thanks packrat for making this so simple.
@backlasae With a small declination number like your area has, over short distances, you won't be very far off base. The longer distance you travel, the more of a difference it makes. If you are not using a map, it is not really necessary to worry with declination either. Thanks for watching!
Yes. It's that simple. I live in NYS and have a westerly declination of 13 degrees so I would add thirteen. When trying to get bearings off a map just use the lines of True North which are always easier to use and then just add or subtract your declination and your on your way. It gives one the ability to use the most basic compass without all those special features. I prefer the military compass which has no declination.
Great video and thank you for the info.
Thanks man, was checking if i got the west is best and east is least correct, liked and subbed.
A fantastic video. Thanks a bunch !!!!
Thank you very much for your video it has been very helpful
@capreolus4 Thanks for the support! I appreciate it!
Thanks, no more confusion!
Very good explanation, thanks for posting.
Awesome presentation.Thanks,
@Lintassimilator Thanks, I tried to put it in when I uploaded, but the upload failed. I will put it in now.
Thanks for the video. Yours made it the easiest with the rhyme. I'm using a compass to set my telescope's base to true North. So if I'm getting this correctly, with my declination at 11° East, my telescope's base should be set to a reading of 349° to be pointing at true North.
@swiftwren Thanks! Your right, I actually recorded that on my computer as an experiment and decided to use it just to do something new. Thanks for noticing!
Cheers mate! well explained look forward to seeing more videos from ya.....catch ya later geezer:)
Great intro vid.
This is very well done. I'm sitting here with my map and SUUNTO compass haha
@him3zz within a mile, normally you can find your destination with a map based on terrain features alone. However, IF you can only use your compass (at night or in a forrest for example), then yes it would make a huge difference. For example, I'm in Utah and I try to find my way from point A to point B with a bearing of 90 deg on a map. The declination is 15 deg. If I did not adjust for this, and went walking at 90 deg (instead of 75 deg). After a mile I would be ~1500ft north of point B.
great video!
Well done!
thanks man..good stuff!
great info to know thanks!
No. It's not even the same across the US. You can find UK declinations at The British Geological Survey website (geomag.bgs.ac.uk), though RUclips won't let me post the URL.
Alternatively, OS maps show the declination for a given date and the expected change per year.
At the moment (2013), there's only a degree or two between grid and magnetic north in most of the UK, so you probably don't need to worry about declination for a few years.
ChaffSorter I don’t worry about it. Unless you up above snow line in Scotland it’s unlikely that with our U.K. figures that it’s worth messing with as most of the time you can pick up a land mark on map and use that as well. Places like the states where the areas are bigger and the figures are more like 10+ degrees it’s worth learning. We’re lucky to have OS and British geological survey here in U.K.
Thank you very much! so helpful!
@DTOlness2860 Thank you! I appreciate it.
Good info! Thx
great videos thanks
Warning...the declination map pictured in the silva instruction book is very old and is wrong...declination changes a little every year...type "declination calculator" in google and you can get the noaa site to get your correct declination.
@PackRat556 Great Video. You explained declination value very well. How would you apply the degrees on the compass itself?
Generally a GPS user, but bought a compass the other day. Would like to become proficient with one. Yours are some great starter videos, PackRat556. Thanks.
Awesome! thank you!
Cheers for the info Pack Rat and i noticed you changed your intro and outro music...
What dose that look like on the compass? Meaning show us on the compass as you're path of travel. How would you turn the ring and what would you follow?
Awesome, so at 5:47, simply subtract the declination from the current bearing and navigate?
outstanding Packrat...where do I sign, for the course..you gotta teach it up man. cheers ;-))
Is true north along the earths axis? or is it the line perpendicular to the plane containing the earths orbit?
useful. very
Seems pretty simple though. If you have an Easterly declination of 10 degrees, you do the math and then you just say ok I'll set my compass to 80 degrees rather than 90 degrees. That's what you would do right? I'm new to this.
Does the values (signs) change if you're in the southern hemisphere?
PACK RAT, I have a question for you. What if - now bear with me - I lived 1 mile of my destination. Would declination still be of relevence? Please respong.
I didn't see this video on your channel.
Mine is -12 W is it still Best even though its a negative
I have a lensatic compass that does not have an adjustable declination. If I understand correctly, I wait until the last step to compensate for declination? For example, if my declination is 40 degrees west, I know that I would add 40 degrees. But I don't adjust for this before orienting the map? I don't account for this before determining a direction of travel? First I orient the map so that north on my compass is north on the map. Next, I draw a line to determine a direction of travel. Then finally, I would add the declination on to whatever bearing I got? Thank you in advance for clarifying for me.
+Phillip Griffin Hello Mr. Griffin. You are mixing to different map and compass techniques that adjust for declination. As described in the video above and using just your lensatic compass: First determine your degree of travel on the map, Second add or subtract your declination value, The new value is your actual Compass Bearing.
A second method to adjust for Declination is called map orientation to the compass. This is done by aligning the North indicator on the Compass and North Marginal lines on the map. First pick a vertical line on the map. Place your compass edge on that vertical line. Second, rotate the map itself with the compass still on top until the Magnetic needle is pointing to the North indicator on the compass. You will know when this is done correctly because the Magnetic needle, Compass north indicator, and the Map's north symbol will all line up in the same direction. Next, Without Moving the Map At All, rotate your compass edge to measure your degree of travel on the map. The Degree of travel displayed is your Compass bearing. When you orientate the map to the compass, the declination is automatically adjusted for, granted that you do not move the map once everything is lined up.
+B Wilson Thank you for the in-depth reply friend. I have done much research in the last few weeks. I was confused about two things. Firstly, if one has to orient the map to north before plotting a bearing. For example, when trying to determine what the bearing between where I am and another point on the map. If the line between where I am and my destination is a 90 degrees bearing. I now realize the angle stays the same no matter which direction the map is facing. Meaning that you never have to orient the map to determine bearing. It doesn't make any difference which way the magnetic needle is pointing. The compass is used like a protector to measure angles so that it doesn't matter if the map points north or south or is on someones back or on a tree or upside down. It was confusing in the video when after he determined his bearing was 90 degrees he rotated the "whole compass and map together" to "actually find out where that direction is". Rotating the compass until the magnetic needle is in the "doghouse" aka the orienting arrow, does nothing to change that the "index line" on his compass still points to a 90 degrees bearing. Putting and keeping the needle in the doghouse lets you stay on your 90 degree course and you don't need to rotate the map for that. What rotating the map does is orient the map so that both you and your map are facing the same direction and is independent of your travel direction.Maybe that's what he meant but it was confusing to me and hopefully anyone that has the same problem as me now understands.
Secondly, I wasn't sure at which stage to adjust for declination. You were right in your first paragraph. When going from map to real world, If my declination is 10 degrees west, then after I determine my bearing is 90 degrees on the map I would add 10 degrees and adjust my compass to a 100 degree bearing. I would then travel on a 100 degree bearing according to my compass. Which is what he did in the video.
A very important distinction about the mnemonic he used, "East means least" and "West means best" is correct when you take a bearing from the map to your compass: However, you have to reverse them when going from real world to the map. For instance, if you have a 10 degree west declination you add 10 degrees when going from map to compass (the real world). But, you subtract 10 when going from compass to map. Let's say there is a barn in front of me and it isn't located on my map and I would like to plot it and my declination is 10 degrees west. First I would aim my compass with direction of travel line pointing towards the barn. Next, while keeping my compass pointed at the barn, I would rotate the dial until the magnetic needle was in the "doghouse". Now I would look at the index line and see what degree it is. Lets say its 100 degrees. I would now SUBTRACT 10 degrees. Plotting this on the map I would draw a line starting from me outward at a 90 degree bearing.
For clarity I must point out that in your second paragraph you described how to orient a map to north and how to take a bearing correctly, but you still have to adjust for declination just like in your first paragraph. It seems counterintuative but try it out as an exercise.
Please reply If anything I said isn't clear or I have made a mistake.
Kind regards
Philip, it's clear from this post that you understand navigation better than 90% of the people making the videos. People should skip watching the videos and just read your comments. They will learn more. =^)
Hi packrat. Good vid but to be honest you explain how to calculate based on a "tric" you do not explain why to add or why to substract. That is the reall essence. The difference in angle from the magnetic bearing compared to the grid bearing. So..you do not add/substract because of the compass best/least thing but for another reason, that...is..in my opinion the real reason. Agree?
The URL you requested was not found on the NGDC Server
A current one is located here;
maps.ngdc.noaa.gov/viewers/historical_declination/
Good video !
Much easier: magnetic-declination.com. Try it. You're welcome.
Here's the latest NOAA declination site. www.ngdc.noaa.gov/geomagmodels/struts/calcDeclination
Gary, your link is dead.
Here's a better one: magnetic-declination.com. Click anywhere on the Google map for the correct nation anywhere in the world.
Could be a better vid if you showed how to adjust declination on the compass so one doesn't have to play math class every time they take a new bearing.
your map said UTM grid; but, you adjusted from True North. Why?
Which North Pole does Santa live at? ;-)
The one in Canada....wait, they're both in Canada right now (although Mag. North is moving towards Russia). You can tell its in Canada, Santa wears Red/White (Canada's colours) and what other passport can get you around in/out of countries THAT quickly...not to mention, he's so damn happy, he has to be Canadian.
lol
Can't even pronounce declination correcly from the beginning - why should anyone stick around for the remainder of the vid?
I despise people like you.
Very good info. simple and to the point......However, you need a new sharpie...
declination we aways gave it the name Magnetic ( variation) when i was flying i must be geting old with all them new names comeing into the world
dont use a topo map's declination values. they're only accurate to the year the map was made and may have shifted several degrees by now.
Maybe a minor point, but you are not pronouncing it correctly, the "e" should be soft, not hard i.e. like the first "e" in the word "decimate"
Audio clip of pronunciation is is here:
thefreedictionary(dot)com/declination
Good vid otherwise, clearly and correctly explained
Don’t try this website during a government shutdown. 😂