Mazamas

If your compass is, ahem, not used very often, you may not be very familiar with its attributes.

A key feature on modern compasses is the ability to adjust for magnetic declination.  After this is set, all bearings are read to true north. 

Without making some adjustment for declination, bearings are read to magnetic north.  Converting them to true north requires some backcountry arithmetic, and while fairly easy in principle, invites error when done rarely and/or under the stress of being lost.

So, you may be wondering, I bought my compass years ago.  Does it even have adjustable declination?  Here’s how to tell:

Look for a tiny brass or copper colored screw, usually on the back of your compass.  Turn this (knife tip works) to adjust declination.

Once it’s set to the local value (in NW Oregon, about 17 degrees east) you should never have to touch it again as long as you hike in this area.

If you are looking to buy a compass with adjustable declination, the Mazamas map geeks highly recommend the Suunto M3.  Read more about this compass here

As many newer smart phones have both excellent screen resolution and GPS capability, a reasonable question is, can my smart phone replace a standalone GPS receiver? The short answer, (at least as of 2012), is probably not. Here are a few reasons why.

Rugged design
Smart phones such as the iPhone are simply not as rugged or waterproof as a dedicated GPS receiver.

Battery life
Smart phones generally are not optimized for continuous GPS use. If you leave the GPS capability turned on continuously, you may find yourself with a dead smart phone in just a few hours. While it’s easy to swap out standard AA batteries on a dedicated GPS, you would probably have to carry a small solar or other type of charger with you to fire up your dead smart phone in the backcountry.

Receiver sensitivity
A dedicated GPS receiver typically has a much better quality antenna that a smart phone, and will thus perform better in challenging conditions such as under heavy tree cover or in a steep canyon.

Lack of a good positional fix
Finally, realize that a smart phone may not accurately fix your position when you are outside of cell phone coverage. This is because cell phones use a technology known as assisted GPS.  This system allows your smart phone to get a position fixed very quickly by using information it receives from nearby cell towers. This works great when the smart phone is within the coverage area. If not, it will not always work.

This information is from the excellent book, Outdoor Navigation with GPS, by Stephen W. Hinch

The backcountry navigator has many options when it comes to buying a compass. The bad news: many of these are inappropriate for wilderness use. The good news: a handful of them are terrific, and one in particular has dropped dramatically in price.

Direct from the Mazamas lead navigation instructor, here’s the scoop on what to buy and what to avoid.  The most important feature of a good compass is adjustable declination! Tip:  If a product description says “fixed declination scale”, avoid it.

Desirable features of a good land navigation compass include:

• adjustable declination (the most important feature!  Did I mention this?)
• a long straight edge for plotting lines on the map
• meridian lines inside the compass bezel
• a clear base plate, so you can see the map through it
• ruler(s) engraved on one or more of the edges, for measuring map distances

Higher end compasses may have the following (optional) whistles and bells:

• a clinometer, for measuring slope angle, especially good for backcountry skiers
• a sighting mirror, which marginally improves accuracy of bearings
• liquid filled housing, to dampen the compass needle

As you might imagine, compasses not suitable for backcountry use have few or none of these features.  Compasses are unsuitable for mountaineering if they:

• are too small for accurate bearings
• do not have meridian lines
• are numbered in 5 degree (or more) increments
• do not have degrees marked from 0 to 360
• have non-transparent housings
• cannot be used for measuring and plotting bearings on a map

Here are three compasses that the Mazamas navi-geeks recommend for wilderness navigation.  Students in any Mazamas class with a navigation component are highly encouraged to buy one of these three. All are sold at REI.  They are listed in general order of price and features.

1) El Cheapo but it works:  Suunto M-2D
This compass has adjustable declination, some bare-bones features and not much else. If you want a compass to keep in the bottom of your pack and don’t plan on using it very often (let’s be honest, that describes most of us!), this would be a good choice.  Cost: $24 at REI

2) Just Right: Suunto M3
This is been my go-to compass for many years, and I love it for lots of reasons.  A unique feature of this compass is its ergonomic design. Having a curve on one end reminds the user that that’s the end that belongs in your hand. This almost eliminates the common problem of holding the compass backwards, which results in an error of 180°. It does not have a clinometer or sighting mirror, but these are two features that I feel are largely unnecessary for the majority of backcountry users.  This compass will best serve the needs of most Mazamas.  Cost: $34 at REI

3) High End with special sauce:  Brunton 15TDCL
This compass has recently seen a dramatic drop in price and can actually be found at Amazon (as of January 2012) for a rather unbelievable $31.  It has a clinometer, liquid housing and sighting mirror.  Normally, compasses with all these features sell for well over $50.  If you’re a backcountry skier, search and rescue team member, or frequent user of a compass and require extremely accurate bearings, this is probably the one for you.  Cost: $42 at REI, $31 at Amazon.  (Heck, now that it’s cheaper than my favorite Suunto M3, I may have to get one myself!)

Here are some photos and brief descriptions of compasses that are not suitable for Mazamas classes. If you have one of these, consider getting one of the ones recommended above. You’ll be happy that you did. 

Lensatic compass – accurate bearings, but no baseplate

Baseplate compass, but without adjustable declination

Baseplate compass with mirror, but without clear baseplate

Some material on this page is from The Mountaineers

Latitude and longitude coordinates are a bit of an enigma.  Everyone has heard of them, but few people know the basics of how they work, let alone how to effectively use them for navigation.

Here is a nice tutorial that lays it all out for you.

UTM coordinates, or (Universal Transverse Mercator) is generally the preferred coordinate system to use for land navigation. 

A metric system developed by the US Army in the 1940s, UTM coordinates it allows you to eyeball your position on a large scale map down to about 100 meter accuracy.
Useful for both your GPS receiver and map reading, a deeper understanding of how the coordinates are derived can be useful.

Have a look at this web page that explains it well!

image from wwwmaptools.com