Compass Requirements - photographs and models included -- MUST READ INFO


We suggest that you print this page and take it with you to the store when purchasing a compass

 

All compasses have a magnetized needle that points north, and have a way to indicate direction of travel. Mountaineering requires a compass with additional qualities. Compasses that hang from parka zippers or hook on watchbands are not suitable for this course or as part of your ten essentials. Good compasses are easily found, but many compasses on the market are not suitable for use in this course.

 

Caution - take care when buying a compass - read this advice first

 

Every year, some students buy unsuitable compasses, usually the result of not following the guidelines below. Often, a sales person (who may or may not know the requirements of a good compass) was asked for advice. To complicate things further, our local outdoor stores sometimes run out of stock of the recommended compasses. Sales people will try to recommend alternatives (mostly unsuitable). They aren't malicious, but in fact are trying to be helpful. In reality, a good mountaineering compass has no substitute. Retailers will carry a variety of compasses, some suitable, some not.

 

Required Features of a Compass for Basic Navigation Course
Seattle Mountaineers

 

1. 

Adjustable declination: A moveable orienting arrow, which provides a built-in declination adjustment. If there is one feature that simplifies map and compass work, this is it. Compasses with adjustable declination can often be identified by the presence of an adjustment screw, usually brass or copper-colored, and a small key attached to the lanyard.

 

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All students MUST have a compass with adjustable declination. The presence of a declination scale does not guarantee that it can be adjusted.

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If you already have a compass without adjustable declination, you may not use it in this course. Recent experience indicates that such compasses detract from the learning experience.

   

2. 

A transparent rectangular base plate with a direction of travel arrow or a sighting mirror.

 

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Transparency allows map features to be seen underneath the compass.

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The rectangular shape provides straight edges and square angles for plotting and triangulating on the map.

 

 

3. 

A bezel (the rotating housing) marked clockwise from 0 to 360 degrees in increments of two degrees or less. In general, bezels should be large to allow use while wearing gloves - the larger size also improves accuracy.

 

 

4. 

Meridian lines: Parallel 'meridian lines' on the bottom of the interior of the circular compass housing rotate with the bezel when it is turned. The meridian lines run parallel to the north-south axis of the bezel, however turned. Meridian lines are necessary for plotting and triangulating on the map.

 

 

5. 

A ruler and/or gradient scale engraved on one or more of the straight edges, used for measuring distances. Compasses with other additional scales facilitate advanced navigation.

 

 

6. 

A 3 to 4-inch base plate. A longer straight edge makes map work easier.

 

 

 

Additional recommendations

 

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A sighting mirror in the cover: This reduces errors introduced when moving the compass from eye-level after sighting to waist-level for reading the dial.

 

 

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A liquid-filled housing to reduce erratic needle movement (only needed on some compasses). In some cases, steadying the compass needle can be difficult

 

 

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An inclinometer: a gravity driven arrow that allows you to measure slope angle.

 

 

 

Current Favorites

 

Current favorites with a sighting mirror include the Suunto MC-2, Silva Ranger CL, as well as Kasper & Richter’s Alpin and Sherpa BW2.  Recommended compasses without a mirror include the Suunto M-3 CM, Silva Explorer, and the Kasper & Richter Horizon.

Please note that not all of these recommended compasses are available at REI. Silva can be purchased online at Campsaver.com, and the Kasper & Richter compasses can be purchased at Backcountry.com (Mountaineer’s members receive a discount at this retailer).  Suunto is currently available at REI and online.  Keep any receipt! We have unfortunately had many defective compasses in the past.

Brunton compasses have also been recommended in the past.  However, their current offerings all now include ‘tool-less declination’ which requires pressing down on the bezel to set the declination.  We have found this to be difficult and may not provide the best accuracy with the declination setting.  While Brunton compasses meet all of the specifications listed above, the tool-less declination makes them less user friendly and we do not recommend using this brand for the class.

 

Keep any receipt! We have unfortunately had many defective or inadequate compasses in the past.

 

Diagram of minimum features:


 

 

Diagram of recommendations:


 

Unacceptable compasses

 

Compasses are unsuitable for mountaineering if they are too small for accurate bearings, do not have meridian lines, are numbered in 5 degree increments, have non-transparent housings, do not have degrees from 0 to 360, or cannot be used for measuring and plotting bearings on a map.

Features which make a compass undesirable or unsuitable:

  • Lack of a straight edge for plotting lines on a map
  • Lack of declination adjustment
  • Lack of meridian lines inside the bezel
  • Small size -- less than 3.5" x 2.2"
  • Small bezel - less than 2" in diameter
  • A dark base plate (you can't see a map through the compass)
  • Poor action/movement (poor mechanics - should be smooth and firm, not loose)

UNSUITABLE compasses for this course:

  • Brunton 26 DNL-CL
  • Brunton model 8020 GPS
  • Suunto KB20/360
  • Suunto MB-6 Matchbox
  • Brunton model 9020 G

Photographs of unacceptable compasses (many of which are commonly sold at local outdoor retailers) - we suggest you look at this link before buying a compass.

 
Unusual compasses
 
There are two unusual compasses offered by Brunton (the eclipse models) which are acceptable, but are not well suited to most mountaineering activities. They are very accurate, and of high quality. We will accept (but not encourage) the use of these compasses in the course.
 
Photographs of the Brunton Eclipse compasses
 
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