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After reading this article you will learn about the uses of compass clinometer, with the help of diagram.
The dip and strike of an exposed bed in the field can be measured in degrees by an instrument, known as a clinometer, which consists of a pendulum with a graduated arc. A compass can measure the directions of the dip and strike similarly.
For the sake of convenience, a clinometer as well as a compass is both combined together, as to form an instrument known as Clinometer-Compass. The clinometer of this instrument will help in measuring the amount of the dip and the strike, while the compass will help in measuring their directions with respect to north, south, east and west.
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The clinometer compass (Fig. 4.3) differs rather from an ordinary compass in the following manner:
(i) This compass is usually fixed to a rectangular plate made of cast iron or plastic, in such a way that the 0° = 180° diameter, i.e., North-South direction, is parallel to the length (i.e., longer side of the rectangular plate).
(ii) The divisions on the circle from 0° to 360° go anti-clockwise. The signs for East and West are thus the opposite from the normal compass. This is done so as to calculate the azimuth of the strike directly from the position of the North = pointing end of the magnetic needle.
(iii) A clinometer is situated to the compass needle with a half circle divided from 0° to 90° on either side, as shown. The angle of the dip is measured by its position on the half circle.
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The elements on the beds of a rock stratum are determined in four steps by this instrument:
(a) The direction or line of the strike is first determined on a cleared patch of the bed.
(b) Having determined the strike, the direction or line of the dip is determined.
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(c) To determine the azimuth of the dip of the bed the compass is applied to the strike, so that the south end is pressed against the bed and the north end is pointed down the dip.
(d) Knowing the azimuth of the dip of the bed, there is no need to further measure the azimuth of the strike, as adding or subtracting 90° to the measured azimuth of the dip can easily calculate it.