1. BRUNTON COMPASS
INTRODUCTION:-
A Brunton compass, properlyknownasthe Brunton Pocket Transit, isa type of precision compass
made by Brunton, of Riverton,Wyoming.Unlikemostmoderncompasses,the BruntonPocketTransit
utilizes magneticinductiondampingratherthanfluidtodampenneedleoscillation.AlthoughBrunton
Inc. makesmanyothertypesof magneticcompasses,the BruntonPocketTransitisa specialized
instrumentusedwidelybythose needingtomake accurate degree andangle measurementsinthe field.
These people are primarilygeologists,butarchaeologists,environmental engineers,and surveyors also
make use of the Brunton'scapabilities.
HOW TO USE:
It maybe adjustedfordeclinationangle accordingtooneslocationonthe earth.Holdingthe compass
at waistheight,the userlooksdownintothe mirrorand linesupthe target,needle,andguidline thatis
on the mirror.Once all three all linedup andthe compassislevel,the readingcanbe made.The strike is
measure byleveling the compassalongthe plane beingmeasured.Dipistakenbylayingside of the
compassperpendiculartothe strikeandrotatinghorizontal level untilthe bubble isstable andreading
has beenmade.
2. COMPONENTS:
It has three mainparts,box,slightarm,and lid.The box containsmostof the elements:the needle,bulls
eye level,clinometerlevel,andclinometerscae,dampingmechanism, liftpin,sidebrassskrew,and
index pingraduatedcircle.The needle hastwoends:the northseekingendandthe blacksouthseeking
end.Anaditional weightattachedtosouthseekingendof the needleprovides properbalancingof the
needle.
APPLICATIONS & importace of brunton compass
1. Determiningthe magnetic declination
If the compassneedle pointseastorwestof the true north,the offsetiscalledeastorwest
declination,respectively.The standardistouse the magneticnorth(MN) as a reference for
declination,eveninthe southern hemisphere
2. Settingthe declination
Geologistsuse the compassformappingandmeasuringlinearandplanarobjects.The
magneticdeclinationissetbyturningthe brassscrew on the side of the compassbox.For a
westdeclinationof say16o
(i.e.,declinationis16o
westof true north),turn the card west,i.e.,
counterclockwise (byturningthe screw)
3. The concept ofdomain
One of the objectivesof studyingacomplexlydeformedarea(e.g.,refoldedfolds) istoidentify
domains(subareas) withinwhichthe fabricdataof,for example,folds,lineations,foliationsare
homogeneous
4. Attitude of linearand planar geological objects
Althoughmostgeologicstructuresare generallyeithercurvilinearorcurviplanar,theycanbe
approximatedaseitherlinearorplanarat specificscalesordomains.
5. Measuringthe attitude of linearobjects
Measuringtrendand plunge:If the linearobjectisbelow ourlineof sight,openthe sighting
arm and the lid,andalignthe open,longslotof the arm parallel tothe linearfeature.If the
linearfeature isabove ourhead(e.g.,ona beddingabove us),standunderthe objectandalign
the linearfeature withthe blackaxial lineonthe mirroron the lidof the compass.
