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A thumb compass is a type of compass commonly used in orienteering, a sport in which map reading and terrain association are paramount. In cases of homogenous terrain with few distinct features, a bearing between 2 known points on the map may be used. Consequently, most thumb compasses have minimal or no degree markings at all, and are normally used only to take bearings directly from a map, and to orient a map to magnetic north. Thumb compasses are also often transparent so that an orienteer can hold a map in the hand with the compass and see the map through the compass. Thumb compasses attach to one's thumb using a small elastic band. The first commercially successful orienteering thumb compass was the Norcompass, introduced by Suunto in 1983.〔http://www.cpearce.orconhosting.net.nz/Archive_AOC/COC_NovDec_83_OCR.pdf〕 "The Gear Junkie," a syndicated newspaper columnist in the United States, has an in-depth review of thumb compasses.〔(The Gear Junkie, September 2005, ''Gear Review: The Thumb Compass'' )〕 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 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. ==See also== *Protractor compass *Hand compass 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「thumb compass」の詳細全文を読む スポンサード リンク
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