Compact magnetic compass
Parts of a hand compass
A
hand compass
(also
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.
[1]
[2]
Hand or sighting compasses include instruments with simple
notch-and-post
alignment ("gunsights"),
prismatic sights
, direct or lensatic sights,
[3]
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.
[4]
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.
[5]
[6]
A
hand compass
may also include the various one-hand or 'pocket' versions of the surveyor's or geologist's
transit
.
History and use
[
edit
]
A standard Brunton Geo, used commonly by geologists
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.
[7]
These soon evolved into more elaborate and specialized models such as the Brunton
Pocket Transit
patented in 1894.
[8]
Hand compasses were soon widely employed in the practice of
forestry
,
geology
,
archaeology
,
speleology
, preliminary
cartography
and
land surveying
.
Compass used by engineering geologists
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
[9]
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.
[10]
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.
[11]
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
.
[12]
[13]
Many models featured an optional
quadrant
(0-90-0 degree) scale instead of an
azimuthal
(0-360 degree) system.
[14]
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.
[15]
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.
Marine hand bearing compass
[
edit
]
Floating-card
compass with prismatic sight (bearing 220° through eyepiece)
The marine hand compass, or hand bearing compass|hand-bearing compass as it is termed in nautical use, has been used by small-boat or inshore sailors since at least the 1920s to keep a running course or to record precise bearings to landmarks on shore in order to determine position via the
resection
technique.
[16]
[17]
Instead of a magnetized needle or disc, most hand bearing compasses feature liquid damping with a
floating card
design (a magnetized, degreed float or dial atop a jeweled pivot bearing).
[18]
Equipped with a viewing prism, the hand bearing compass allows instant reading of forward bearings from the user to an object or vessel, and some provide the reciprocal bearing as well.
[19]
[20]
Modern examples of marine hand bearing compasses include the
Suunto KB-14
and
KB-77
, and the
Plastimo Iris 50
.
[21]
[22]
These compasses frequently have battery-illuminated or
photoluminescent
degree dials for use in low light or darkness.
[23]
[24]
Notes
[
edit
]
- ^
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
- ^
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).
- ^
Suunto Oy,
The Suunto KB-14 Story
,
Article
Archived
2008-04-09 at the
Wayback Machine
- ^
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.
- ^
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
- ^
Hudson, William J.,
The Brunton Pocket Transit
, 26 January 2005
Article
- ^
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.
- ^
Rutstrum, pp. 47-55, 64-72
- ^
Bonner Soil & Water Conservation District,
Idaho State Forestry Contest
(October 2004), p. 25
Article
Archived
2008-12-15 at the
Wayback Machine
- ^
Nix, Steve,
The Best Forestry Field Compass
Article
Archived
2008-08-07 at the
Wayback Machine
- ^
Suunto Oy,
The Suunto KB-14 Story
- ^
Rutstrum, pp. 47-55, 197-199
- ^
Rutstrum, p. 72
- ^
Casey, Don,
Using a Hand Bearing Compass
Article
- ^
Seidman, David,
The Complete Sailor: Learning the Art of Sailing
, McGraw-Hill Professional (1995),
ISBN
0-07-057131-7
,
ISBN
978-0-07-057131-0
, pp. 190-194
- ^
Dickison, Dan,
Powerboat Reports Guide to Powerboat Gear: Take the Guesswork Out of Gear Buying
, Globe Pequot Press (2006),
ISBN
1-59228-069-2
,
ISBN
978-1-59228-069-8
, pp. 91-93
- ^
Seidman, pp. 190-194
- ^
Dickison, pp. 91-93
- ^
Suunto Oy,
The Suunto KB-14 Story
- ^
Dickison, pp. 91-93
- ^
Dickison, pp. 91-93
- ^
Suunto Oy,
The Suunto KB-14 Story
References
[
edit
]
- Avery, T.E., Burkhart, H.E.,
Forest Measurements
, 5th ed. New York:McGraw-Hill (2002)
- Johnson, Mark,
The Ultimate Desert Handbook: A Manual for Desert Hikers, Campers, and Travelers
, McGraw-Hill Professional (2003),
ISBN
0-07-139303-X
, 9780071393034
- Mooers Jr., Robert L.
Finding Your Way In The Outdoors
, Outdoor Life Press (1972),
ISBN
0-943822-41-6
- Rutstrum,
The Wilderness Route Finder
, University of Minnesota Press (2000),
ISBN
0-8166-3661-3
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