1. prepared
By
Prof. Karm Balar

2.  The types of compass that are used
commonly are:
 (i) prismatic compass
 (ii) surveyor compass.

4.  Define:-compass graduation disc is fixed to the box and
magnetic needle is free to rotate above it.
 (1).is balanced on a hard and pointed steel pivot
 (2). The top of the pointed pivot is protected with agate cap
 (3).An aluminium graduated disk
 (4) is fixed to the top of the needle.
 (5) hinged to the box. In the centre the slit is provided with a
horse hair or a fine wire or thread
 (6). The metal frame is provided with a hinged mirror
 (7), which can be placed upward or downward on
the frame. It can be slided along the frame.
 (8) with a sighting eye vane
 (9). The prism magnifies the readings on the graduation disk
justbelow it.

5.  (10). Dark sunglasses
 (11) provided near the line of sight can be interposed if
the object to be
sighted is bright (e.g., sun).
 (12) which is about 85 mm to 110 mm supports the pivot of
needle firmly
at its centre.
 (13) lid which protects the graduation disc at the same
time permit the direct reading from
the top.
 (14) which activates
lifting lever
 (15) lifts the needle off the pivot.
 (16). For pressing spring a knob
or brake pin
 (17) is provided on the box. When not in use prism can be
folded over the edge of the box.

6.  an instrument used in surveying for measuring horizontal
angles — compare CIRCUMFERENTOR 1, SEMICIRCUMFERENTOR
 In this type of compass graduation disc is fixed to the box
and magnetic needle is free to rotate above it.
There is no prism provided at viewing end, but has a
narrow slit. After fixing the line of sight, the reading is
directly taken from the top of the glass cover.

8.  Meridian is a reference direction with
respect to which the direction of lines are
mentioned.
 There are three types of meridian - True
Meridian, Magnetic Meridian & Arbitrary
Meridian

9.  1 - True Meridian
 It is the reference direction of north pole of
earth from a given station point. It is also called
geographic meridian.
 2 - Magnetic Meridian
 It is the direction of north pole indicated by
magnetic needle.
 3 - Arbitrary Meridian
 This is any assume direction to a well defined
object. It may be useful for small areas.Direction
of magnetic north with respect to true north is
called magnetic direction.

10.  Bearing is the angle which a certain line
make with a certain a certain meridian.
 Bearing with respect to true meridian is
called true bearings while magnetic bearing
is the angle which a line makes with respect
to magnetic meridian.
 There are two ways to represent the
bearings,

11.  1) Whole Circle Bearing (W.C.B)
 It can be taken 0° to 360°. Quadrants are
taken clock-wisely and angles are also
determined in clockwise direction.
 2) Reduced Bearing
 Reduced bearing or Quadrantal bearing is the
angle which a line makes from North or South
Pole whichever may be near. It is value is
from 0° to 90°.

13. Whole Circle Bearing (W.C.B) Reduced Bearing (R.B)
135° S45E
37° N37E
65° N65E
125° S55E
215° S35W