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10.3 E h’s
of o on
The Earth rotates about its polar (north-south) axis in 24 hours, rotating from West to East at a rate of approximately 15 0 /hour. The duration of a solar day is 24 hours, the time taken for an Earth fixed object to point directly at the Sun. The time taken for the Earth to rotate to the same orientation in space, known as the Sidereal day, is 23 hours 56 min 4.1 seconds. The Earth rotates through one geometric revolution each Sidereal day, not in 24 hours, which accounts fo h slgh lys ng lu ofE h’s ; 15.041067 0 /hour. Anypon on h E h’ssuf c smo ng n c cul cb c us h E h sspnnngon s xs h s . h d c onof h spn co nypon on h E h sp ll l o h xsof o on, . . h E h’spol xsd fned by the geographic North and South poles.
A nypon on h E h’ssufc, h E h
c n b sol d n o ho zon l nd
c l compon n s s
illustrated below.
Figure 52: Calculating the Earth’s rate of rotation.
h ho zon l compon n of E h’s
lw yspons ow ds h g og phc o h ol ndd fn s
f nc
direction to which the orientation of the survey tool can be measured using a gyroscope.
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