Reading A Lensatic Compass

Question 0

Bezel ring

Answer 0

The bezel holds the upper glass crystal in place. It helps preset a direction for night Compass navigation. It contains 120 clicks when fully rotated; each click equals 3°

Question 1

Compass dial

Answer 1

Floats free when in use. It is locked in place by closing the eyepiece. It contains two complete circular scales, one in degrees (read scale) and one in Mils (black scale). The magnetic arrow is found on the Compass

Question 2

Cover

Answer 2

The cover contains a sighting wire. When closed it protects the face of the Crystal. When at a 90° angle to the other half of the Compass, it can be used to sight on objects.

Question 3

Thumb loop

Answer 3

Retaining device to secure the Compass in a closed position. Used when holding the Compass in position for sighting on objects.

Question 4

Black index line

Answer 4

Stationary line used as a reference for determining direction. When held properly, it identifies the direction the Compass is pointing.

Question 5

Sighting wire

Answer 5

Provides an exact azimuth for objects. Can be used for compass calibration. Also used with steering marks.

Question 6

The declination diagram

Answer 6

Indicates the difference between true North, grid north, and magnetic north. Used when converting a magnetic azimuth shown on your lensatic compass dial to a grid azimuth on your map. You can also use it to convert a grid azimuth a magnetic as well. The declination diagram is different for every map

Question 7

True North

Answer 7

Indicates the direction of the geographic North Pole. True North is marked by a star (*) on the declination diagram

Question 8

Grid north

Answer 8

Indicates the direction in which the north-south gridlines of a map are oriented. These may not or may correspond with true or magnetic north, depending on where you are located in the world

Question 9

Magnetic north

Answer 9

In the case the north direction of your Compass reading. It is usually different than true North because the earths magnetic field causes the Compass arrow to point to a magnetic area around instead of directly at the north pole. Magnetic north direction will change depending on your geographic location and also with time. Magnetic north is marked with a half arrowhead

Question 10

G-M angle

Answer 10

The difference between grid North and magnetic north shown in degrees You will add or subtract this value from the magnetic or grid azimuth when converting from one direction to another.

Question 11

Orienting the map

Answer 11

Adjusts the map so that north on the map points to North on the ground and the information on the map will match the features on the ground

Question 12

Orienting a map

Answer 12

Step one) determine the direction of magnetic north and the G-M angle on the declination diagram
Step two) align the straightedge on the Compass with a north-South grid line
Step three) rotate the map and compass together aligning the magnetic Arrow and the fixed black index line
Step four) rotate the map and compass together until the Compass arrow is aligned with the magnetic arrow
Step five) check the Compass reading

Question 13

Holding a Compass

Answer 13

The two most common are the center hold technique and the compass to cheek technique

Question 14

Center hold technique

Answer 14

Fast and easy. Used under any visibility conditions without taking off your helmet or removing your rifle from sling arms.

Question 15

Center hold technique

Answer 15

Open the Compass, set the lens (rear site), position your thumb, position your fingers, position your elbows.

Question 16

Compass to cheek technique

Answer 16

More accurate and ideal when employing intersection and resection techniques and are more accurate azimuth required.

Question 17

Compass to cheek technique

Answer 17

Position the cover, fold the rear site, align the front site hairline, read the azimuth

Question 18

Determining an azimuth

Answer 18

Raise the Compass to Eye level, aligned the center of the siding slot, read the azimuth

Question 19

Determining the azimuth

Answer 19

The azimuth, in degrees, is the red number on the dial lying directly under the black line of the Compass Crystal. The azimuth, in Mils, is the black number on the outer perimeter of the doubt

Question 20

Selection and use of steering marks

Answer 20

It will defined guiding object on the azimuth. Can be natural or man-made but fixed and stable. While navigating, day or night, every step you take should be toward a selected steering Mark.

Question 21

Setting a course

Answer 21

Set the azimuth directly under the black index line (Holding the Compass in this position, rotate the bezel ring until the luminous indicator is over the North arrow of the dial. The direction indicated by the open Compass is the desired course)
Rotate the bezel to North arrow (Holding them and set a compass in this position, rotate the bezel ringing until the luminous indicator is over at the North arrow of the doubt. The direction indicated by the open Compass is the desire course)

Question 22

Proceeding along an azimuth

Answer 22

Align the magnetic compass arrow with the luminous line, proceed forward towards the desired as well, select a steering Mark

Question 23

Looking positions by means of intersecting azimuths

Answer 23

Used to locate distant or inaccessible points or objects such as enemy danger areas. There are two methods of intersection: the map and compass method and the straight edge method.

Question 24

Map and compass method

Answer 24

Orient map, Mark your position on the map, determine the magnetic azimuth, convert the magnetic azimuth, draw a line on the map, move to a second known point, determine the grid coordinates

Question 25

Straight edge method

Answer 25

Compass not available.
Orient the map, locate your position, rotate using a straight edge, draw a line, repeat to next position, determine coordinates

Question 26

Dead reckoning

Answer 26

Follow the desired as much on your Compass, while keeping a pace count until you have traveled the distance to your destination

Question 27

Pace count

Answer 27

A pace Count is equal to two natural steps, about 60 inches long or 1.5 m. To accurately use pace count method, you must know how many paces it takes to walk 100 m. A pace is counted whenever your left foot touches the ground

Question 28

Shifting techniques

Answer 28

Combination of Compass azimuth and knowledge of intended route.

Question 29

Checkpoints

Answer 29

Checkpoints are typically terrain or man-made features design as such in planning. Line checkpoint is far superior to a point checkpoint for navigation at night.

Question 30

Interference and accuracy

Answer 30

Vulnerable to iron and powerlines that emit electromagnetic fields

Question 31

Limitations

Answer 31

55 m high extension powerlines
10 m field gun, truck or tank
10 m telegraph/telephone wires or Barbwire
2 m machine gun
.5 m steel helmet or rifle

Question 32

Inspections

Answer 32

Inspect whenever you use Compass. Inspect floating dial to ensure that the glass and crystal parts are not broken, the numbers on the dial are legible, the floating doubt does not stick, the sighting wire is straight, the bezel ring produces distinct clicks turn

Question 33

Care and maintenance

Answer 33

Rinse with freshwater, especially after exposure to salt water
Brush off dirt and grime
Ensure the ridges on the bezel ring are free of dirt
Check movement of the rear sight to ensure it is free moving