A thumb compass is a type of compass

Compass

A compass is a navigational instrument that shows directions in a frame of reference that is stationary relative to the surface of the earth. The frame of reference defines the four cardinal directions – north, south, east, and west. Intermediate directions are also defined...

 commonly used in orienteering

Orienteering

Orienteering is a family of sports that requires navigational skills using a map and compass to navigate from point to point in diverse and usually unfamiliar terrain, and normally moving at speed. Participants are given a topographical map, usually a specially prepared orienteering map, which they...

, a sport in which map reading and terrain association are paramount. Consequently, most thumb compasses have minimal or no degree markings at all, and are normally used only to orient the map to magnetic north. Thumb compasses are also often transparent so that an orienteer can hold a map

Map

A map is a visual representation of an area—a symbolic depiction highlighting relationships between elements of that space such as objects, regions, and themes....

 in the hand with the compass and see the map through the compass.

Thumb compasses attach to one's thumb

Thumb

The thumb is the first digit of the hand. When a person is standing in the medical anatomical position , the thumb is the lateral-most digit...

 using a small elastic

Elastomer

An elastomer is a polymer with the property of viscoelasticity , generally having notably low Young's modulus and high yield strain compared with other materials. The term, which is derived from elastic polymer, is often used interchangeably with the term rubber, although the latter is preferred...

 band.

The first commercially successful orienteering thumb compass was the Norcompass, introduced by Suunto in 1983.

"The Gear Junkie," a syndicated newspaper columnist in the United States, has an in-depth review of thumb compasses.

Placing an even greater emphasis on speed over accuracy, the wrist compass lacks even a baseplate, consisting solely of a needle capsule strapped to the carpometacarpal joint

Carpometacarpal joint

The carpometacarpal joints are five joints in the wrist that articulates the distal row of carpal bones and the proximal bases of the five metacarpal bones....

 at the base of the thumb; the thumb serves the function of a baseplate when taking and sighting bearings. It is often used for city and park race orienteering

Orienteering

Orienteering is a family of sports that requires navigational skills using a map and compass to navigate from point to point in diverse and usually unfamiliar terrain, and normally moving at speed. Participants are given a topographical map, usually a specially prepared orienteering map, which they...

.

External links

• Silva 6 Jet Spectra, a typical modern thumb compass
• The Internet Compass Museum gives comprehensive information about all sorts of compasses and how to use them.