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A hand compass (aka hand bearing compass or sighting compass) is a compact magnetic compass capable of one-hand use and fitted with a sighting device to record a precise bearing or azimuth to a given target or to determine a location.〔Frazer, Persifor, ''A Convenient Device to be Applied to the Hand Compass'', Proceedings of the American Philosophical Society, Vol. 22, No. 118 (Mar., 1885), p. 216〕〔SCFC, ''Get Acquainted With Forestry Tools'' (Article )〕 Hand or sighting compasses include instruments with simple notch-and-post alignment ("gunsights"), prismatic sights, direct or lensatic sights,〔Johnson, Mark, ''The Ultimate Desert Handbook: A Manual for Desert Hikers, Campers, and Travelers'', McGraw-Hill Professional (2003), ISBN 0-07-139303-X, 9780071393034, p. 134: A ''direct-sighting'' compass uses a magnifying viewfinder mounted in the compass body to directly view a degreed dial and superimposed indicator line; it therefore differs from a ''lensatic sight'' (which uses a simple magnifying lens on a folding arm positioned over the dial), or a ''prismatic sight'' (which uses a magnifying optical prism).〕 and mirror/vee (reflected-image) sights. With the additional precision offered by the sighting arrangement, and depending upon construction, sighting compasses provide increased accuracy when measuring precise bearings to an objective.〔Suunto Oy, ''The Suunto KB-14 Story'', (Article )〕 The term ''hand compass'' is used by some in the forestry and surveying professions to refer to a certain type of hand compass optimized for use in those fields, also known as a forester or cruiser compass.〔Rutstrum, ''The Wilderness Route Finder'', University of Minnesota Press (2000), ISBN 0-8166-3661-3, pp. 47-55, 64-72〕〔Mooers Jr., Robert L. ''Finding Your Way In The Outdoors'', Outdoor Life Press (1972), ISBN 0-943822-41-6, p. 47: The term ''cruiser compass'' derives from the practice of foresters ''cruising'' or estimating the value of a stand of timber by taking compass readings to ascertain the size of the stand.〕 A ''hand compass'' may also include the various one-hand or 'pocket' versions of the surveyor's or geologist's transit. ==History and use== While small portable compasses fitted with mechanical sighting devices have existed for a few hundred years, the first one-hand compass with a sighting device appeared around 1885.〔Frazor, Persifor, ''A Convenient Device to be Applied to the Hand Compass'', Proceedings of the American Philosophical Society, Vol. 22, No. 118 (Mar., 1885), p. 216〕 These soon evolved into more elaborate and specialized models such as the Brunton ''Pocket Transit'' patented in 1894.〔Hudson, William J., ''The Brunton Pocket Transit'', 26 January 2005 (Article )〕 Hand compasses were soon widely employed in the practice of forestry, geology, archaeology, speleology, preliminary cartography and land surveying. In the United States, the hand compass became very popular among foresters seeking a compass to plot and estimate stands of timber. While the ''Pocket Transit'' was more than adequate for such work, it was relatively expensive. Consequently, a new type of hand compass was introduced: the ''forester'' or ''cruiser compass''. Traditionally, ''cruiser'' compasses featured a sighting notch, a mechanically-damped〔Mooers Jr., Robert L. ''Finding Your Way In The Outdoors'', Outdoor Life Press (1972), ISBN 0-943822-41-6, pp. 48-49: Most of the traditional designs used a momentary button lock mechanism that froze the needle in position to stop excessive swing and permit a reading.〕 or "dry" needle, adjustable declination and a large dial marked in individual degrees using counterclockwise calibration (reversed east and west positions). A screw base for a tripod or ''jacob staff'' (monopod) was often fitted as well.〔Rutstrum, pp. 47-55, 64-72〕 By the late 1960s many foresters had begun using more modern liquid-damped compass designs, including mirror-sight protractor models such as the ''Silva Type 15 ''Ranger'''' or the ''Suunto MC-1'' (later, the ''MC-2''). These compasses were fast to use, particularly along straight cruise lines and were sufficiently accurate for most forestry applications.〔Bonner Soil & Water Conservation District, ''Idaho State Forestry Contest'' (October 2004), p. 25 (Article )〕 On the other hand, geologists, speleologists, archaeologists, ornithologists, and foresters engaged in precision survey work often used direct-reading models such as the ''Suunto KB-14'', prismatic compasses such as Suunto ''KB-77'' or the traditional Brunton ''Pocket Transit''.〔Nix, Steve, ''The Best Forestry Field Compass'' (Article )〕〔Suunto Oy, ''The Suunto KB-14 Story''〕 Many models featured an optional quadrant (0-90-0 degree) scale instead of an azimuthal (0-360 degree) system.〔Rutstrum, pp. 47-55, 197-199〕 By using a hand compass in combination with aerial photographs and maps a person can determine his/her location in the field, determine direction to landmarks or destinations, estimate distance, estimate area, and find points of interest (marked boundary lines, USGS marker, plot centers). For increased accuracy, many professional hand compasses continue to be fitted with tripod mounts.〔Rutstrum, p. 72〕 While the hand compass continues to be widely employed in such work, it has been increasingly supplanted in recent years by use of the GPS, or Global Positioning System receiver. 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「Hand compass」の詳細全文を読む スポンサード リンク
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