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SoM > TC 3-25.26 Map Reading & Land Navigation > Flashcards

TC 3-25.26 Map Reading & Land Navigation Flashcards

1
Q

Q. What FM covers “Map Reading and Land Navigation?”

A

A. TC 3-25.26 (All references now reflect this change.)

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2
Q

The art and science of expressing the known physical features of the earth graphically by maps and charts is known as what?

A

Cartography. (ch 2, introduction)

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3
Q

What is a map?

A

A map is a graphic representation of a portion of the earth’s surface drawn to scale, as seen from above. (para 2-1)

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4
Q

In the division, who is responsible for map requisitions and distribution?

A

This is the responsibility of the G2 section. (para 2-5)

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5
Q

All maps should be considered as documents requiring special handling, and should not fall into enemy hands. Why is this?

A

If a map falls into unauthorized hands, it could easily endanger military operations by providing information of friendly plans or areas of interest to the enemy. Even more important would be a map on which the movements or positions of friendly soldiers were marked. It is possible, even though the markings on a map have been erased, to determine some of the erased information. (para 2-6)

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6
Q

If a map is no longer needed, it must be turned in to the proper authority. If a map is in danger of being captured, it
must be destroyed. What is the best method for destroying a map if this becomes necessary?

A

By burning it and scattering the ashes. If burning is not possible, the map can be torn into small pieces and scattered
over a wide area. (para 2-6)

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7
Q

What should you keep in mind if you have to trim the margins of a map for any reason?

A

Be sure to note any marginal information that may be needed later, such as grid data and magnetic declination.
(para 2-7)

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8
Q

What organization provides mapping, charting, and all geodesy support to the armed forces and all other national
security operations?

A

The NGA

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9
Q

What does NGA stand for?

A

National Geospatial-Intelligence Agency (para 2-3)

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10
Q

Military maps are categorized by what two things?

A

Scale and type. (para 2-8)

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11
Q

What is meant by the “scale” of a map?

A

The scale is expressed as a representative fraction (RF) and gives the ratio of map distance (numerator) to ground distance (denominator). (para 2-9)

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12
Q

NGA maps are classified by scale into what three categories?

A
  • Small scale (1:1,000,000 and smaller)
  • Medium scale (larger than 1:1,000,000 but smaller than 1:75,000)
  • Large scale (1:75,000 and larger)
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13
Q

What is the standard “small scale” map and what is it used for?

A

1:1,000,000; it is used for general planning and for strategical studies where very large land areas need to be displayed, but at the expense of detail.

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14
Q

What is the standard “medium scale” map and what is it used for?

A

1:250,000; used for operational planning. (para 2-10)

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15
Q

What is the standard “medium scale” map and what is it used for?

A

A. 1:250,000; used for operational planning. (para 2-10)

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16
Q

What is the standard “large scale” map and what is it used for?

A

1:50,000; used for tactical, administrative, and logistical planning. (para 2-10)

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17
Q

What are some of the different TYPES of maps produced by the NGA?

A
  1. Planimetric – no contour lines
  2. Topographic – has contour lines
  3. Digital Maps – a visual representation depicted by electronic data compiled into a virtual image
  4. Digital city graphic – shows the locations of important buildings, airfields, military installations, embassies,
    hospitals, schools and other structures
  5. Photomap – map information (grid lines, scale, etc) superimposed on an aerial photograph
  6. Joint Operations Graphics (JOGs)
  7. Photomosaic – assembly of aerial photographs
  8. Terrain Model – scale model of the terrain
  9. Military City – map showing the details of a city, with street names, important buildings, and other elements of
    the urban landscape important to navigation and military operations in urban terrain.
  10. Special – special maps that usually include information not found on standard maps
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18
Q

Where does a map get its name and where is the “sheet name” located?

A

A map is generally named for the largest settlement contained within the area covered by the sheet, or for the largest natural feature located within the area at the time the map was drawn; the sheet name is found in bold print at the center of the top and in the lower left area of the map margin. (para 3-1)

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19
Q

What are the colors used to facilitate the identification of features on a standard large-scale topographic map?

A

• Black – indicates cultural (man-made) features such as buildings and roads, surveyed spot elevations, and all labels.
• Red-Brown – the colors red and brown are combined to identify cultural features, all relief features, non-surveyed
spot elevations, and elevation, such as contour lines on red-light readable maps.
• Blue – identifies hydrography or water features such as lakes, swamps, rivers and drainage.
• Green – identifies vegetation with military significance, such as woods, orchards and vineyards.
• Brown – identifies all relief features and elevation, such as contours on older edition maps, and cultivated
land on red-light readable maps.
• Red – classifies cultural features, such as populated areas, main roads and boundaries on older edition maps.

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20
Q

Q. What is meant by the “military grid reference system?”

A

It is a network of squares formed by north-south, east-west lines superimposed on a geographic projection.

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21
Q

Q. What is the principle for reading grid coordinates on military maps?

A

RIGHT and UP. (para 4-9)

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22
Q

What is the distance between grid lines on a standard large-scale map?

A

Normally 1,000 meters (1 km) (para 4-11)

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23
Q

How many digits are required to locate a point to within 100 meters?

A

6 (para 4-13)

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24
Q

How many digits are required to locate a point to within 10 meters?

A

8 (para 4-14)

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25
Q

How many digits are required to locate a point to within 1 meter?

A

10

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26
Q

The graphic scale is divided into two parts. What are they?

A

Primary scale (to the right of the zero) and the extension scale (marked in tenths to the left of the zero). (para 5-7)

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27
Q

Directions are expressed as units of angular measure. Name three common units of angular measure used by
military personnel.

A 
(para 6-1)
• Degree – 360 degrees in a circle (when subdivided into minutes and seconds, one degree equals 60 minutes
and one minute equals 60 seconds)
• Mil – 6,400 mils in a circle
• Grad – 400 grads in a circle
28
Q

Define the term “azimuth”?

A

A horizontal angle measured clockwise from a north base line. (para 6-3)

29
Q

What is a “back azimuth” and how is it obtained?

A

It is the opposite direction of an azimuth. To obtain the back azimuth from an azimuth:
• If the azimuth is less than 180°, add 180°
• If the azimuth is more than 180°, subtract 180° (para 6-3)

30
Q

What is the back azimuth of 20°?

A

200°

31
Q

What is the “declination diagram” and where is it located?

A

This diagram shows the relationship between true north, magnetic north and grid north; it is located in the lower
margin on most larger maps. Medium-scale maps may show declination information by a note in the map margin.
(para 6-10, 6-11)

32
Q

What is the Grid-Magnetic (G-M) angle used for and where is it located?

A

It is used in converting from grid north to magnetic north and vice-versa; it is found in the declination diagram.
(para 6-11)

33
Q

What is meant by “intersection?”

A

This is a method used to determine the location of an unknown point by successively occupying at least two (preferable three) known positions on the ground and then map sighting on the unknown location. (para 6-17)

34
Q

What is meant by “resection?”

A

This is a method used to locate one’s position on a map by determining the grid azimuth to at least two well-defined locations that can be pinpointed on the map. (para 6-18)

35
Q

What are the four types of compasses described in TC 3-25.26?

A

Lensatic (M1) compass, artillery M2 compass, wrist/pocket compass, and protractor. (para 8-1)

36
Q

What are the three major parts of the lensatic compass?

A

Cover, base and lens. (para 8-2)

37
Q

There are two scales on a lensatic compass; the outer scale, normally in _______ (color) denotes ______ and
the inner scale, normally in _______ (color) denotes _______.

A

Black, mils; red, degrees. (para 8-2)

38
Q

The bezel ring on the base of a lensatic compass is a ratchet device that clicks when turned. It contains ______
clicks when rotated fully through 360°; each click is equal to about _____ degrees. What is its primary purpose?

A

120; 3; for use at night (if you need to make a 30° turn, rotate the bezel ring 10 “clicks” in the desired direction).
(para 8-2)

39
Q

What are the two approved techniques for holding the compass when sighting?

A

Centerhold and compass-to-cheek. (para 8-7)

40
Q

Name three field expedient methods for determining the four cardinal directions.

A

Shadow-tip method, watch method, and star method

41
Q

What is “elevation”?

A

The vertical distance above or below the datum plane (usually mean sea level). (para 9-1)

42
Q

What is “relief”?

A

The representation (as depicted by the mapmaker) of the shapes of hills, valleys, streams, or other terrain features on the earth’s surface. (para 9-1)

43
Q

What are the five methods of depicting relief?

A

Layer tinting, form lines, shaded relief, hachures, and contour lines. (para 9-3)

44
Q

Which of the above methods is the most common on standard topographic maps?

A

Contour lines. (para 9-8)

45
Q

What are “contour lines”?

A

Imaginary lines on the ground that connect points of equal elevation. (para 9-8)

46
Q

What are the three types of contour lines?

A

(para 9-8)
• Index - heavy lines; normally every fifth contour line is an index contour. They are usually numbered at some
point with the elevation of points along that line.
• Intermediate - the lighter contour lines falling between index contours. There are normally four intermediate
contour lines between index contours.
• Supplementary - resemble dashes; show changes in elevation of at least one-half the contour interval; normally
found where there is very little change in elevation, such as on fairly level terrain.

47
Q

What are the five MAJOR terrain features?

A 
(para 9-26)
• Hill
• Ridge
• Valley
• Saddle
• Depression
48
Q

What are the three MINOR terrain features?

A

(para 9-32)
• Draw
• Spur
• Cliff

49
Q

What are the two SUPPLEMENTAL terrain features?

A

(para 9-36)
• Cut
• Fill

50
Q

What is the best way to orient a map without a compass?

A

By aligning the features on the map with the same features on the ground (terrain association). (para 10-10)

51
Q

What four units of measure are most commonly used on military maps and can be found in the Graphic (Bar)
Scales?

A
  • Statute miles
  • Nautical miles
  • Yards
  • Meters
52
Q

Explain the shadow-tip method of determining direction.

A

• Step 1: Place a stick or branch into the ground at a level spot where a distinctive shadow will be cast. Mark the
shadow tip with a stone, twig, or other means.
• Step 2: Wait 10 to 15 minutes until the shadow tip moves a few inches. Mark the new position of the shadow
tip in the same way as the first.
• Step 3: Draw a straight line through the two marks to obtain an approximate east-west line.
• Step 4: Place your left foot on the first mark and your right foot on (or in line with) the second mark. North will
be to your front, south to your rear, west on your left side, and east on your right side.

53
Q

Q. What is a simple rule to remember if you are uncertain which mark is east and which is west?

A

A. The sun always rises in the East and sets in the West. The shadow will move in the opposite direction – so the first
shadow-tip mark is always in the west direction, anywhere on earth (except as noted below). (para 8-18)

54
Q

Explain the watch method of determining direction.

A

• In north temperate zones, the hour hand is pointed toward the sun. A south line can be found midway between
the hour hand and 1200 hours (standard time, or 1300 hours for daylight savings time).
• In south temperate zones, the 1200-hour dial is pointed toward the sun, and halfway between 1200 hours
(standard time, or 1300 hours for daylight savings time) and the hour hand will be a north line.

55
Q

Using the watch method for determining direction can cause circling, especially in the lower latitudes. What can
you do to prevent this?

A

Make a shadow clock and set your watch to the time indicated. Check and reset every hour. (para 8-21)

56
Q

Less than _____ of approximately 5,000 stars visible to the eye are used by navigators. The stars seen as we look
up at the night sky are not evenly scattered across the whole sky. Instead, they are in groups called _____________.

A

60; constellations. (para 8-22)

57
Q

Where can the North Star be found?

A

It is the last star in the handle of the “Little Dipper.” (para 8-24)

58
Q

Two stars in the Big Dipper are a big help in trying to locate the North Star. What are they called?

A

The “Pointers.” An imaginary line drawn through them five times their distance points to the North Star. (para 8-24)

59
Q

Joint Operations Graphics, or JOGs, are normally based on what size (scale) military topographic maps?

A

1:250,000 (para 2-10)

60
Q

JOGs are produced in what two formats? What is the major difference?

A

JOG (Air) and JOG (Ground); the topographic information is identical on both, but the ground version shows elevations
and contour in meters and the air version shows them in feet. Both versions emphasize airlanding facilities, but
the air version has additional symbols to identify aids and obstructions to air navigation. Each version is identified in
the lower margin as either Joint Operations Graphic (Air) or Joint Operations Graphic (Ground). (para 2-10)

61
Q

What are some examples of “special” military maps?

A

Maps designed specifically to show one or more of the following: (para 2-6b(8))
• Drainage characteristics • Electric power
• Climate • Fuels
• Coasts and landing beaches • Water resources
• Urban areas • Natural construction materials

62
Q

When military maps are not available, substitute maps may have to be used. What are some examples of substitute maps?

A
  • Foreign maps • Atlases
  • Tourist road maps • Field sketches
  • City/utility maps
63
Q

__________ is the degree of conformity with which horizontal positions and vertical values are represented on a
map in relation to an established standard.

A

Accuracy (para 2-12)

64
Q

List some of the items of information that may be contained in the margin of a military map.

A

Sheet name; sheet number; series name; scale; series number; edition number; index to boundaries; adjoining
sheets diagram; elevation guide; declination diagram; bar scales; contour interval note; spheroid note; grid note; projection
note; vertical datum note; horizontal datum note; control note; preparation note; printing note; grid reference
box; unit imprint and symbol; and the legend. (para 3-1)

65
Q

Where is the sheet number found on a military map?

A

In bold print in both the upper right and lower left areas of the margin, and in the center box of the adjoining sheets
diagram (which is found in the lower right margin). (para 3-1)

SoM (13 decks)

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