That's how I do it too. Nine times out of ten it's all you need. But if you really need to remember I use the mnemonic MATS = map add terrain subtract. Even a scatter brain like me can remember MATS
Allowing for true north!!
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That's how I do it too. Nine times out of ten it's all you need. But if you really need to remember I use the mnemonic MATS = map add terrain subtract. Even a scatter brain like me can remember MATS
Haha, one of the good things about where I am right now:
You clicked here:
Latitude: 52° 9' 19.4" N
Longitude: 5° 22' 5.5" E
Magnetic declination: 0° -0' EAST
Declination is POSITIVE
You clicked here:
Latitude: 52° 9' 19.4" N
Longitude: 5° 22' 5.5" E
Magnetic declination: 0° -0' EAST
Declination is POSITIVE
although without this skill you are also in trouble, working on just topography is not much use at night, serious fog, or serious snow.
good thread though people. remember you pacing. always remember your pacing.
You can always change to a military compass and use the mils systems for increased accuracy, degrees is far harder to use over longer legs as your needle covers a large part of the compass card, keep the legs shorter and map to ground more with pacing 100 m distances using pebbles or ranger beads or time inc naysmiths rule.
Couple of little points.
The needle numbers tend to relate to continents and all that differs is the weighting of the needle as mentioned so it doesn't foul the capsule not allowing it to fully rotate. This is due to the curvature of the earth and topo surface, as the earth is not flat the needle is never point in the x,y plane to the pole You can buy global compass where the needle is average and the capsule enlarged so it does not foul.
mils does not provide a more accurate system that degree this is a fallacy, mils are used in the military as a convenient way of measuring off set and distances as 1 mil subtended at a Km covers 1m.
Hope this helps all the posts that explain that true north isnt of much use are correct declination isnt so much of an issue and its the GMA you want, when it is of use is when you calculate your local decilination on the ground and wish to convert this to magnetic and grid norths.
The needle numbers tend to relate to continents and all that differs is the weighting of the needle as mentioned so it doesn't foul the capsule not allowing it to fully rotate. This is due to the curvature of the earth and topo surface, as the earth is not flat the needle is never point in the x,y plane to the pole You can buy global compass where the needle is average and the capsule enlarged so it does not foul.
mils does not provide a more accurate system that degree this is a fallacy, mils are used in the military as a convenient way of measuring off set and distances as 1 mil subtended at a Km covers 1m.
Hope this helps all the posts that explain that true north isnt of much use are correct declination isnt so much of an issue and its the GMA you want, when it is of use is when you calculate your local decilination on the ground and wish to convert this to magnetic and grid norths.
although without this skill you are also in trouble, working on just topography is not much use at night, serious fog, or serious snow.
good thread though people. remember you pacing. always remember your pacing.
Aye, fair point, those are the times that sort the map readers from the crow bait for sure.
I'm a bit confused with the terminology in use. my understanding
the effect of the north pole and the magnetic pole not being in the same place = variation
the effect of any magnetic interference locally = deviation
the fact that the pull of magnetic north is not parallel to the earths surface = declination
or is the nautical and terrestial usage different
Boatswain
Variation west compass best
the effect of the north pole and the magnetic pole not being in the same place = variation
the effect of any magnetic interference locally = deviation
the fact that the pull of magnetic north is not parallel to the earths surface = declination
or is the nautical and terrestial usage different
Boatswain
Variation west compass best
The difference between magnetic and grid bearings is called magnetic variation in Britain and declination in the US.
The higher scale maps have vertical lines printed on them, for ease of printing and because most people do not know any difference, lines on maps are printed parallel, when they should slightly converge to wards the north (top) of the map.
It also helps to know where true north is, so you can take into account both facts when plotting or triangulating your place
thanks tadpole for the clarification of the terms.. got to pull you up on this though
[ lines on maps are printed parallel, when they should slightly converge to wards the north (top) of the map. ]
Lines on maps are printed parallel because maps use a mercator projection. ( http://en.wikipedia.org/wiki/Mercator_projection ) Unless your travelling long distances and using great circles to navigate or near the poles this does not generally make any practical difference.
I can now also report that what I thought was declination some people may refer to as dip http://en.wikipedia.org/wiki/Magnetic_dip not really something to worry about most of the time.
Boatswain
[ lines on maps are printed parallel, when they should slightly converge to wards the north (top) of the map. ]
Lines on maps are printed parallel because maps use a mercator projection. ( http://en.wikipedia.org/wiki/Mercator_projection ) Unless your travelling long distances and using great circles to navigate or near the poles this does not generally make any practical difference.
I can now also report that what I thought was declination some people may refer to as dip http://en.wikipedia.org/wiki/Magnetic_dip not really something to worry about most of the time.
Boatswain
Jungle re how can you say that mils is not more accurate if there is 17.7 mils to a degree and 6400 mils to 360 degree, ive used mils systems all my long colourful career and used degrees on escape and evasion and found it to be lacking the accuracy.
A brief history of mils: A “mil” is a unit of angular measurement. The military’s use
of mils, which was used to help direct artillery fire, goes back as far as the late 1800’s.
Its modern form of use by the military for directing fire was developed in the 1950’s. The
modern “mil” is short for milliradian, a trigonometric unit of angular measurement.
It is finer in measurement than degrees, thus more precise. In shooting, we can use mils
to find the distance to a target, which we need to know, to adjust our shot. It is also used
to adjust shots for winds and the movement of a target.
Jay
A brief history of mils: A “mil” is a unit of angular measurement. The military’s use
of mils, which was used to help direct artillery fire, goes back as far as the late 1800’s.
Its modern form of use by the military for directing fire was developed in the 1950’s. The
modern “mil” is short for milliradian, a trigonometric unit of angular measurement.
It is finer in measurement than degrees, thus more precise. In shooting, we can use mils
to find the distance to a target, which we need to know, to adjust our shot. It is also used
to adjust shots for winds and the movement of a target.
Jay
Have a shuffty at the picture on this page OS It show clearly what I was saying/meant about how important it is to know the difference between what is real and what it printed on the maps.
Ok not so critical for the south of England, but up north, there is a noticeable difference.
I guess it explains why a fair few yachter run out of fuel when heading for the Scilly Isles
Quite easily as each degree brakes down into 60 minutes which then each one brakes down into 60 seconds. Thus when accurate measurement are needed the degrees system is used
As said before mils was adopted by the military becouse the angle subtends to 1m at a click. the measurement doesnt exist elsewhere and originated from a basterdisation of Rads. A miltary mil is not directly the same as a milliradian (although the difference is tiny).
Mils are convenient because one mil subtends one metre at one km, but they are no more accurate than degrees for practical navigation purposes.
You may well have 17.7 mils to a degree, but you can't actually set a bearing of 14 mils on a compass -- the graduations are not fine enough to take advantage of the precision.
I don't have a compass graduated in mils, haven't used on since I got out of the army, and I don't know what the interval of the graduations is. But my compass is graduated at two-degree increments, which means that's as precise as I can ever be. Anything between the graduations is a guess.
The additional precision that mils give you is an illusion.
You may well have 17.7 mils to a degree, but you can't actually set a bearing of 14 mils on a compass -- the graduations are not fine enough to take advantage of the precision.
I don't have a compass graduated in mils, haven't used on since I got out of the army, and I don't know what the interval of the graduations is. But my compass is graduated at two-degree increments, which means that's as precise as I can ever be. Anything between the graduations is a guess.
The additional precision that mils give you is an illusion.
Andrew have you tryed one of these
http://cgi.ebay.co.uk/Brass-Militar...kparms=72%3A1229|66:2|65:12|39:1|240:1318
the Additional precision that mils gives you which is a illusion to you will be helped by the additional 35.54 mils to your 2 degree graduation.
Armley white, no mate Marines for 15 years recce trp/sniper/recce leader/bpt, now bubble head working mct. you serving???
Jungle re liked your stuff you made on bcl, love to try that leather work out. can you pm me a list of stuff i would need to start out if i have not insulted you with my rantings.
Jay
http://cgi.ebay.co.uk/Brass-Militar...kparms=72%3A1229|66:2|65:12|39:1|240:1318
the Additional precision that mils gives you which is a illusion to you will be helped by the additional 35.54 mils to your 2 degree graduation.
Armley white, no mate Marines for 15 years recce trp/sniper/recce leader/bpt, now bubble head working mct. you serving???
Jungle re liked your stuff you made on bcl, love to try that leather work out. can you pm me a list of stuff i would need to start out if i have not insulted you with my rantings.
Jay
No, Not any more. Started out in 45 rgmnt then onto 7RHA, but was seconded to 29rgmnt during the South Atlantic fracas. Served in various places and ended up in Larkhil as instructor in Gunnery.
Well you cant teach a old dog new tricks, Ive used the mils system in brunei and belize in some hairy primary jungle and happy using pacing, altometer and a silva (in mils) and i trust it, If im getting into 1 second of angle i must be right in the pXXh, last time someone was talking about 1 second of angle i was in a moa (minute of angle) lecture on my snipers course in Lympstone. Bad memories. Nice to meet you Armley white. Thanks for the kit list Jungle re!!
Jay
Jay
No, my experience is with a Silva Ranger, in mils, which is the standard Canadian army compass.
Your additional precision is an illusion, whether you want to admit it or not. I can set a bearing of 13.5 degrees on a compass graduated in degrees, but that's really just a guess, an approximation. I'm just shy of the 14 degree mark and calling it 13.5.
Similarly, you can try to set a bearing of 238.95 mils on a compass graduated in mils, but it is an approximation.
Approximations are not precise, by definition. And then you introduce the additional errors of reading the compass, which is never 100% precise, and errors in following the bearing, again never 100 % precise.
I like using mils. It's a good system. But navigation with a hand-held compass necessarily involves approximation, which kills the additional precision of your 6400-mil circle. The compass you link to is graduated in 100 mil increments. How precise do you think you can really be?
At the end of the day, trying to hit something bang on using a compass bearing alone over distance in testing conditions and wild terrain isn't as easy as the text books suggest and requires more tools in the navigation skills tool box to be used to get it right, ie, aspect of slope, using the contours, aiming off, target approaches, handrails, time and distance, tick off points, etc - you get a group of students to undertake the same leg between two features using a compass bearing and they will all have different outcomes - keep it simple.
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