Compasses with more than 3° + variation should not be used.ĭ. However, a compass has to be checked periodically on a known line of direction, such as a surveyed azimuth using a declination station. A compass in good working condition is very accurate. Telegraph or telephone wires and barbed wire ……………. The following separation distances are suggested to ensure proper functioning of a compass: However, nonmagnetic metals and alloys do not affect compass readings. Metal objects and electrical sources can affect the performance of a compass. The user must also make sure the sighting wire is straight, the glass and crystal parts are not broken, the numbers on the dial are readable, and most important, that the dial does not stick.ī. One of the most important parts to check is the floating dial, which contains the magnetic needle. A detailed inspection is required when first obtaining and using a compass. COMPASS HANDLINGĬompasses are delicate instruments and should be cared for accordingly.Ī. This scale can be used with a 1:50,000-scale map, but the values read must be halved. Some older compasses will have a 1:25,000 scale. The rear sight must be opened more than 45° to allow the dial to float freely. The rear sight also serves as a lock and clamps the dial when closed for its protection. The lens is used to read the dial, and it contains the rear-sight slot used in conjunction with the front for sighting on objects. (4) The thumb loop is attached to the base of the compass.Ĭ. A short luminous line that is used in conjunction with the north-seeking arrow during navigation is contained in the glass face of the bezel ring. It contains 120 clicks when rotated fully each click is equal to 3°. (3) The bezel ring is a ratchet device that clicks when turned. (2) Encasing the floating dial is a glass containing a fixed black index line. There are two scales the outer scale denotes mils and the inner scale (normally in red) denotes degrees. The arrow always points to magnetic north and the letters fall at east (E) 90° and west (W) 270° on the dial. Printed on the dial in luminous figures are an arrow and the letters E and W. (1) The floating dial is mounted on a pivot so it can rotate freely when the compass is held level. The body of the compass contains the following movable parts: It contains the sighting wire (front sight) and two luminous sighting slots or dots used for night navigation.ī. The compass cover protects the floating dial. The lensatic compass ( Figure 9-1) consists of three major parts: the cover, the base, and the lens.Ī. However, it should be noted that when using the protractor on a map, only grid azimuths are obtained. A protractor can be used to determine azimuths when a compass is not available. It contains a north-seeking arrow and a dial in degrees. The wrist/pocket compass is a small magnetic compass that can be attached to a wristwatch band. The artillery M2 compass is a special-purpose instrument designed for accuracy it will be discussed in Appendix G. It is discussed in detail in paragraph 9-2. The lensatic compass is the most common and simplest instrument for measuring direction. This chapter describes the lensatic compass and its uses, and some of the field expedient methods used to find directions when compasses are not available. To complement these techniques, a mastery of field movement techniques is essential. Part One of this manual discussed the techniques of map reading. Soldiers should be thoroughly familiar with the compass and its uses. PART TWO LAND NAVIGATION Chapter 9 NAVIGATION EQUIPMENT AND METHODSĬompasses are the primary navigation tools to use when moving in an outdoor world where there is no other way to find directions.
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