Is there a "right" kind of compass?

[Neil]

It's always interesting how discussions like this one inevitably lead to "gps vs. map and compass".

I get much more satisfaction out of getting from A to B successfully with M&C than with gps. But, for some long, complicated bushwhacks that require fairly precise checkpoints and route changes the gps is a great backup. If used in lieu of M&C the gps saves time (at least in my case).

There's something special and undefinable that I like about pre-trip map study, then reading the terrain, reading the map and using the compass, perhaps an altimeter and a watch.

What is really cool is recording your route on a gps and viewing it on the computer afterwards.

 

[sardog1]

No, you'll substract the declination in Jackman - here's a reference.

Sorry, but this is an example of why the mnemonic tricks often fail. The correct answer to onstep's question is indeed to ADD the declination.

The USGS has published this lesson to help:

How To Use a Compass with a USGS Topographic Map

Method #1: (these directions assume your orienting arrow lines up with the North indicator on your compass dial, meaning the compass has not been adjusted for declination).

A) Obtain the local magnetic declination for the area represented on your map. At the bottom of every USGS map is a diagram that displays the difference & direction between true north (represented as a star), grid north (abbreviated as “GN”), and magnetic north (abbreviated as “MN”). Magnetic declination is the number of degrees and direction between true north and magnetic north. Because declination varies over time, it is advisable to get a reasonably current figure. If your USGS map is more than 15 years old (the declination date appears in the diagram), here’s an easy-to-use website that gives you only the information you need for your specific area:

http://gsc.nrcan.gc.ca/geomag/field/mdcalc_e.php

If magnetic north is east of true north, the local declination is positive.

If magnetic north is west of true north, the local declination is negative. (NOTE: This is the situation in Maine and all the rest of the Northeast.)

B) Draw a line on the map that connects your starting point with the destination (your “map bearing”). Extend the line all the way through the map border (the “neat line”).

C) Distance yourself from any nearby metal such as keys, belt buckle, desk, car, fence, etc. Place the compass on the map so the needle’s pivot point is directly over the intersection of your map bearing and neat line.

D) Rotate the dial until compass ring north agrees with map north. Read your map bearing from the compass dial. Make sure the bearing agrees with your direction of travel – for example, if you intend to travel due east, the bearing is 90 degrees, not 270 degrees.

E) Do this step mentally – don’t turn the compass dial. If the local declination is positive, then subtract the declination amount from the bearing you just derived. If the local declination is negative, then add the declination amount to the bearing you just derived. (So, if you're in Jackman, Maine, where the declination is negative (i.e., the magnetic needle points to the left of true north), then you'll ADD to the map bearing.)

F) Turn the compass dial until the figure you calculated in step E lines up with the index line.

G) Lift the compass off the map, and with the direction of travel arrow pointing directly away from you, rotate your body and the compass all in one motion until the red magnetic needle overlays the orienting arrow.

H) Sight a landmark along this bearing, and proceed to it. Repeat this step until you reach your destination.

Method #2: (these directions assume your orienting arrow lines up with the North indicator on your compass dial, meaning the compass has not been adjusted for declination).

A) Obtain the local magnetic declination for the area represented on your map. At the bottom of every USGS map is a diagram that displays the difference & direction between true north (represented as a star), grid north (abbreviated as “GN”), and magnetic north (abbreviated as “MN”). Magnetic declination is the number of degrees and direction between true north and magnetic north. Because declination varies over time, it is advisable to get a reasonably current figure. If your USGS map is more than 15 years old (the declination date appears in the diagram), here’s an easy-to-use website that gives you only the information you need:

http://gsc.nrcan.gc.ca/geomag/field/mdcalc_e.php

If magnetic north is east of true north, the local declination is positive

If magnetic north is west of true north, the local declination is negative.

B) Draw a line on the map that connects your starting point with the destination (your “map bearing”).

C) Distance yourself from any nearby metal such as keys, belt buckle, desk, car, fence etc.

D) Place the compass on the map so the baseplate is parallel to the line you drew. Make sure the direction of travel arrow points to your destination.

E) Rotate the dial until compass ring north agrees with map north. Do not move the compass when you rotate the dial.

F) Remove the compass from the map and, with the direction of travel arrow pointing directly away from you, rotate your body and the compass all in one motion until the red magnetic needle overlays the orienting arrow.

G) If local declination is positive, then subtract the declination amount (turn the dial clockwise). If local declination is negative, then add the declination amount (turn the dial counter-clockwise). (Again, if you're in Jackman, Maine, where the declination is negative (i.e., the magnetic needle points to the left of true north), then you'll ADD to the map bearing.)


H) Again, with the direction of travel arrow pointing directly away from you, rotate your body and compass all in one motion until the red magnetic needle overlays the orienting arrow. Sight a landmark along this direction of travel and proceed to it. Repeat this step until you reach your destination.

 

[Nessmuk]

I have a drawer full of maps with red parallel magnetic north lines on them. It's a night before the 'whack tradition.

This morning I'm heading up to Jackman for 3 days of bushwhacking. I'm going to try something different. My compass does not have an adjustable declination feature. I'm going to use the *true* north grid lines from the map. That means when I set a bearing from the map I'll have to add the declination to the compass... Add Map to Compass... AMC right?

Onestep

What map has *true* north grid lines already on it? If you are using a USGS topo map, do not confuse the UTM grid lines with true north, they are not the same. The only true north on the map is at the edges, the longitude meridians. There may be 4 "+" marks also on the map interior that you can draw meridians and parallels through, but no grid lines. For practical purposes you may get away with using the UTM grid lines, as by definition they are never more than +/- 3 degrees from true.

To use another reference system, use logic instead of forgettable word games that can get you off course by double the declination if not applied correctly. Think of where on the globe the magnetic north pole is in Canada... thus if I am east of Chicago then the magnetic north lines tilt left. The little diagram on the bottom of some (not all) topo maps depicts this graphically.

Therefore, if I am actually facing true north, then my compass needle will point to my left, and after "boxing the needle" I will be reading, say for example, 014 degrees (the map's published declination) on the compass. That concept of what your compass reads when you face true north gives you the answer and a way to logically convert to any other direction.

This means if I want to head in the direction of 000 true, I must go in the direction of 014 magnetic by my compass. If I want to travel 020 true, then I must go 020+014=034 magnetic. If I want to travel 270 true, then I must set the compass to 270+014=284 magnetic. To go 350 true, set 350+14=004. Simple and unforgettable because you know how to derive the answer with logic, not memory.

I find it far easier to do my map study, draw the mag north lines, and there's my reference permanently set. No math, no converting to another reference system, no fuss, no errors at the end of a long day's slog through the woods.

 

[DougPaul]

What map has *true* north grid lines already on it? If you are using a USGS topo map, do not confuse the UTM grid lines with true north, they are not the same. The only true north on the map is at the edges, the longitude meridians. There may be 4 "+" marks also on the map interior that you can draw meridians and parallels through, but no grid lines. For practical purposes you may get away with using the UTM grid lines, as by definition they are never more than +/- 3 degrees from true.

There is grid north, true north, and magnetic north. All different. (All should be shown in the declination diagram on USGS topos.) Grid north is usually close enough to true north in the continental US for hikers to use either one. (The difference is larger in northern Alaska and northern Canada.)

<logic snipped> Simple and unforgettable because you know how to derive the answer with logic, not memory.

Different methods work best for different people. I personally like logic, others prefer rules-of-thumb. I prefer to hold a map north-up and rotate to match the world in my head, others perfer to rotate the map to match the world. Whichever--as long as it works when you need it.

I find it far easier to do my map study, draw the mag north lines, and there's my reference permanently set. No math, no converting to another reference system, no fuss, no errors at the end of a long day's slog through the woods.

Remember that conditions where you really need the compass may include fatigue, panic, zero visibility, wind, precip, threat of hypothermia, etc. It becomes easy to make a mistake under these conditions (particularly when using logic or rules of thumb) and therefore I think that it is a good idea to use methods which eliminate the need for the conversion: ie automatic declination on the compass (my preference) or predrawn magnetic north lines (Nessmuk's preference).

Ultimately the goal is not my method is better than your method or for everyone to use a single method--it is for everyone to have a bomb-proof method that works for them when needed.

KISS (Keep It Simple Stupid).

Doug

 

[Rick]

Sorry, but this is an example of why the mnemonic tricks often fail. The correct answer to onstep's question is indeed to ADD the declination....

Hence my earlier comment that it takes work, knowledge and PRACTICE to really operate a compass. It is easy to learn this stuff but if you don't use it or practice it for 4-5 years and then find that all you can remember is "East is Least West is Best" (I think that even came in my Silva Ranger Compass directions), you might be in trouble - Then again, as Sardog mentions, Call someone on your cellphone and have them honk a horn from the Trailhead!!

 

[DougPaul]

Then again, as Sardog mentions, Call someone on your cellphone and have them honk a horn from the Trailhead!!

Not foolproof either--sound does not always travel in nice straight lines. I have been at sea in a heavy fog when the sound of a lighthouse horn would seem to come from one direction at one moment and then from another a bit later.

Sound can be bent by wind and thermal gradients and reflects off large objects.

Doug

 

[DougPaul]

The USGS has published this lesson to help:

How To Use a Compass with a USGS Topographic Map
<snip>

While I'm sure this lesson is quite accurate, it is rather complex. An occasional compass user, even with some initial practice, is likely to have difficulty remembering it sometime later under stressful conditions.

And the statement

If magnetic north is east of true north, the local declination is positive.
If magnetic north is west of true north, the local declination is negative.

is just a rule-of-thumb with no memonic to help one remember it. (I have trouble remembering it here at my keyboard, let alone in the woods.)

Again, I vote for KISS (Keep It Simple Stupid). (See my post #44.)

Doug


PS. This thread has come a long way from "recommendations for a beginner's compass".

 

[sardog1]

While I'm sure this lesson is quite accurate, it is rather complex. An occasional compass user, even with some initial practice, is likely to have difficulty remembering it sometime later under stressful conditions.

And the statement
is just a rule-of-thumb with no memonic to help one remember it.

Again, I vote for KISS (Keep It Simple Stupid).

Doug

I agree that the lesson is complicated. I posted it only to document step-by-step why onestep should be adding at Jackman.

In order of complexity, here's how to deal with declination:

1. Draw the north lines on the map and fuhgedaboudit.

2. Buy a compass with a set screw compensation and remember to set it properly any time you change locations by a signficiant east-west difference, e.g., from NH to ME or VT to NH.

3. Buy a compass with a compensation in the dial that you set by turning a capsule in the dial. Remember to set it properly and to check it while you're in the field in case you move the compensating capsule.

4. Admit you're a masochist and practice using the USGS lesson. Remember that to go from map to compass and compass to map are the opposite and require opposite compensations.

5. Use a mnemonic and carry extra food and water for the inevitable occasion(s) when you mess up.

 

[Nessmuk]

Again, I vote for KISS (Keep It Simple Stupid).

In the final analysis, ALWAYS navigate by making sense out of the terrain and observational clues provided to you. Only when paddling in a dense and overcast fog on a vast windless lake do you only have the compass to follow. Terrain navigation clues abound with every step here in the NE woods. If any one of them does not make sense with the others (including the compass), stop and figure out why not before proceeding. Learn how to spot and correct errors early. Making sense out of your sourroundings is the most basic of all KISS navigation principles.

 

[Nessmuk]

PS. This thread has come a long way from "recommendations for a beginner's compass".

That's because there is so much more critical information necessary to successful navigation than picking out the "right" compass.

 

[DougPaul]

In the final analysis, ALWAYS navigate by making sense out of the terrain and observational clues provided to you. Only when paddling in a dense and overcast fog on a vast windless lake do you only have the compass to follow. Terrain navigation clues abound with every step here in the NE woods. If any one of them does not make sense with the others (including the compass), stop and figure out why not before proceeding. Learn how to spot and correct errors early. Making sense out of your sourroundings is the most basic of all KISS navigation principles.

Of course--always use multiple sources of navigation info if they are available to you.

But the thread topic was choosing a compass (affected by issues of how to use it), not general priciples of navigation.

Doug

 

[ksullnh]

On a separate note, if your background is in sailing, it's important to note that the "declination" we landlubbers refer to is usually "variation" on a boat.

As far as correcting compass error, which is the goal, I tend to use the colorful PG-13 sailing term, "True Virgins Make Dull Company, Add Whiskey" which tells you the order: True, Variation (hike declination), Magnetic (North), Deviation (the effects of the boat or other metal stuff on the magnetic compass), Compass (the bearing on the compass at the helm). "Add Whiskey" means "Add West"....

There shouldn't be any deviation in the woods, unless you have a really big belt buckle from an ultramarathon/rodeo, old school steel exterior frame pack, or are under a radio tower, so Magnetic and Compass are synonymous.

So if your hike-declination (variation) is listed as 16 degrees west, you add it to true north if you're going from left to right ((T->V->M/C) True North - Compass reading), or subtract it if you go from right to left (T<-V<-M/C). The corollary would be to subtract east land-declination (variation) when going from T->M/C, or add when going from M/C->T.

This is probably confusing, so any erstwhile sailors can pull out their Bowditch for a more thorough explanation.

have fun,

kevin

PS: the more G-rated mnemonic is "Can Dead Men Vote Twice, At Elections?" for Compass, Deviation, Magnetic, Variation, True... Add East.

 

[Paradox]

Dear Toe Cozy,
Many handheld GPS units have an integral fluxgate compass. The compass in my Garmin 60CSx is somewhat more stabile in non-level conditions than the Timex watch I bought about 5 years ago and the Auto-Helm flux-gate hand bearing compass I bought about 10 years ago when I was an avid around-the-bouys small sailboat racer. Magellin claims that their compasses have excellent non-level stability. I have a Magellin Platinum that has a very stabile flux-gate compass (though I may have used it twice at most). The compass in my Garmin Vista is horrible and will vary 90 degrees of heading with 5 degrees of tilt. Pick up a 60CSx and see if you use the compass alot or use the GPS most of the time.

 

[DougPaul]

On a separate note, if your background is in sailing, it's important to note that the "declination" we landlubbers refer to is usually "variation" on a boat.

To complete the list of confusing terms, there is also magnetic inclination (or dip angle)--the (vertical) tilt angle of the field. 0 deg at the magnetic equator, 90 deg at the magnetic poles.

A non-zero inclination will push one needle point up and the other down and could cause it to drag on the compass capsule. To prevent this, the earth has been divided into 5 zones, and compass needles have been balanced to work with each zone. Thus, a compass bought for use in N America may not work in S America. Some manufacturers make a "global" compass (eg http://www.rei.com/online/store/Pro...&parent_category_rn=4500598&vcat=searchrefine) which can be used anywhere.

Most users need not worry about this issue--all of the US (except Hawaii), Canada, Euope, and northern Asia are in the same zone and compasses sold within the zone will work within it.

For more info including zone maps see http://www.wide-screen.com/support/FAQsuunto.shtml

Doug

 

[DougPaul]

Many handheld GPS units have an integral fluxgate compass. The compass in my Garmin 60CSx is somewhat more stabile in non-level conditions than the Timex watch I bought about 5 years ago and the Auto-Helm flux-gate hand bearing compass I bought about 10 years ago when I was an avid around-the-bouys small sailboat racer. Magellin claims that their compasses have excellent non-level stability. I have a Magellin Platinum that has a very stabile flux-gate compass (though I may have used it twice at most). The compass in my Garmin Vista is horrible and will vary 90 degrees of heading with 5 degrees of tilt. Pick up a 60CSx and see if you use the compass alot or use the GPS most of the time.

Garmin claims +-2 degree accuracy (+- 5 deg in extreme northern and southern lattitudes) with proper calibration for both the Vista and 60CSx. (They don't say if you need to bring a bubble level with you...)

The batteries in a GPS are magnetic, so there is a simple calibration procedure to calibrate the compass any time the batteries are changed or disturbed. (Currents in the wires also creat small magnetic fields which might also degrade accuracy.)

Magellan uses a 3-dimensional sensor and I have read on sci.geo.satellite-nav that Garmin uses a 2-dimensional sensor. (The eTrex Vista, but not the 60 series existed at the time. I have seen no comments on the 60 series sensors.) If this is indeed true, a GPS with a 2D sensor would be more sensitive to orientation than a GPS with a 3D sensor.

For comparison, when I make sightings with my magnetic compass (Silva Ranger CL, mirror, auto-declination, http://www.rei.com/online/store/Pro...&parent_category_rn=4500598&vcat=searchrefine) whose accuracy can be checked, my error is generally less than a degree.

The magnetic compass on a GPS significantly increases the battery drain--most users turn it off except when actually using it.

Doug

 

[sardog1]

There shouldn't be any deviation in the woods, unless you have a really big belt buckle from an ultramarathon/rodeo, old school steel exterior frame pack, or are under a radio tower, so Magnetic and Compass are synonymous.

Well, almost. There are many places in North America with known anomalies, i.e., places where a compass needle will point somewhere other than magnetic north. From Magnetic Declination -- Frequently Asked Questions, by Chris M. Goulet, Alberta, Canada:


A few areas with magnetic anomalies (there are thousands more):

-North of Kingston, Ontario; 90° of anomalous declination.
-Kingston Harbor, Ontario; 16.3° W to 15.5° E of anomalous declination over two kilometers (1.2 miles); magnetite and ilmenite deposits.
-Near Timmins, Ontario, W of Porcupine.
-Savoff, Ontario (50.0 N, 85.0 W). Over 60° of anomalous declination.
-Michipicoten Island in Lake Superior (47.7 N, 85.8 W); iron deposits.
-Near the summit of Mt. Hale, New Hampshire (one of the 4000-footers, near the Zealand Falls hut on the Appalachian Trail) ; old AMC Guides to the White Mountains used to warn against it. (Not just "old" WMG warnings. In the 27th edition, p. 177: "Many of the rocks around the former fire tower are reputed to be strongly magnetic." Anybody have any anecdotes to relate?)
-Around Georgian Bay of Lake Huron.
-Ramapo Mountains, northeastern New Jersey; iron ore; compass rendered useless in some areas.
-Near Grants, New Mexico north of the Gila Wilderness area; Malpais lava flows; compass rendered useless.

The USGS declination chart of the USA (GP-1002-D) shows over a hundred anomalies. The following table lists the most extreme cases.

Anomalous declination(degrees) Lat. Long. Location

46.4 W -- 40.2 106.2 75 km.(45 mi.) W Boulder, Colorado
24.2 E -- 40.7 75.3 20 km. (12 mi.) NE Allentown, Pennsylvania
16.6 E to 12.0 W over 10km(6mi) -- 46.7 95.4 250 km. (150 mi.) NW Minneapolis, Minnesota
14.8 E -- 33.9 92.4 85 km. (50 mi.) S Little Rock, Arkansas
14.2 E -- 45.5 82.7 In Lake Huron, Ontario
13.8 W -- 45.7 87.1 Escanaba, on shore of Lake Michigan
13.7 E -- 48.4 86.6 In Lake Superior, Ontario
13.5 E -- 48.5 122.5 80 km. (50 mi.) N Seattle, Washington
13.0 W -- 42.2 118.4 In Alvord Desert, Oregon
12.2 W -- 38.9 104.9 10 km. (6 mi.) W Colorado Springs, Colorado
11.5 E -- 47.8 92.3 120 km. (75 mi.) N Duluth, Minnesota

 

[DougPaul]

A few areas with magnetic anomalies (there are thousands more):

The Katahdin tableland is also reported in older copies of the Maine Mtn Guide to have magnetic anomalies. We were required to carry wands when we were there in winter (~1980).

Doug

 

[TomD]

I have a small collection of compasses. My favorite is a Silva 27-a small mirror compass. I also have a Suunto MC-2G which works anywhere (N or S hemisphere) because the needle is weighted for either and a couple of other little ones.

A good book is the Sierra Club's Land Navigation Handbook by W.S. Kals; also check out this website- http://www.learn-orienteering.org/old/ for some basic lessons and also check out the various orienteering sites for info on thumb compasses they use during orienteering races.

Remember, a GPS unit may be more accurate and easier to use, but a compass won't ever run out of power. Once you know how to use a compass and map, getting lost shouldn't be a worry.

 

[nickdu]

There are different kinds of compasses too.

I use a
Brunton 8096

Jay

On the link you provided it shows that compass as Brunton 8096 Eclipse Compass. On REI I see a Brunton 8096-AR. I assume they are the same. I do see an Eclipse on REI but it's a 8099.

 

[Pete_Hickey]

Just about any compass will w2ork, as long as you don't get a Tate's. They are the worst.