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Section
Key Points
1 Marginal Information
2 Topographic Symbols
3 Terrain Features
4 Determining Four- and Six-Digit Grid Coordinates
INTRODUCTION TO
MAP READING
Tactics and
Techniques Track
With our military forces dispersed throughout the world, it
is necessary to rely on maps to provide information to
our combat elements and to resolve logistical operations
far from our shores. Soldiers and materials must be
transported, stored, and placed into operation at the
proper time and place. Much of this planning must be
done using maps. All operations require a supply of
maps; however, the finest maps available are worthless
unless the map user knows how to read them.
FM 3-25.
e
Tactics and Techniques Track
Introduction
In Section 1, you learned how to navigate using information from a civilian-style map and a compass. In doing so, you learned that in order to navigate accurately, the map is one of your most important pieces of equipment. In this section, you will examine a military map, study its parts, and learn more about its uses. To be safe in a battle zone, you must know how to read a map, plot your location, and move in the right direction. If you can’t navigate correctly, you risk getting lost—or worse, stumbling into dangerous territory. Consider the experience of MAJ Robert K. Wright Jr., historian for XVIII Airborne Corps. MAJ Wright accompanied the Corps in Operation Just Cause, the American liberation of Panama in 1989.
Lost in Panama
I had one last interview to do on [January] 13th[, 1990]…. So I went over and got
that interview; they were off at a different location, so I'd gotten a driver to take
me over, and I got one of their drivers to take me back to Fort Clayton, to the
battalion headquarters. And I'd really gotten to know that battalion … very, very
well while I was down there. So I asked the S-3 could he get me a ride to the
airport. So he gave me an NCO and a driver and a 'Hummer' [HMMWV; M-998-
series High Mobility Multi-Wheeled Vehicle] and said “Sure, just take the Doc out.”
So we swung by, picked up my gear. I cleared post. And off we went. And we're
driving and driving and driving, and I know it isn't that far. Plus, we're going
through the jungle. We're going up a paved highway and everything, but passing
traffic and whatnot, which is taking forever. And then we went past this one area
and I recognized it from aerial recon that I had done in the helicopter photography
missions—this was Cerro Tigre, the PDF [Panamanian Defense Force] supply depot.
Which was about 120 degrees in the wrong direction from the airport.
So at that point I casually inquired of the driver “Do you know where we're
going?” And he said, “Why no, sir, I thought you knew where we're going.” And I
turned around and looked at the NCO, and he said “Don't look at me, I don't
have a map either.” So I said “Oh, O.K., well, hang a right and we'll keep going
until we find the ocean or something and we get oriented.” And we literally
wandered around.
And I remembered thinking at the time, yeah, I've got seven rounds in my..
... So here we are, traveling through the countryside and had... I mean, we
were out in the boonies. And had there been a disgruntled PDF guy still running
around loose, it was me and my seven rounds from the .45, and that's all we had
to protect us.
Department of the Army, XVIII Airborne Corps
Introduction to Map Reading ■ 179
Introduction to Map Reading ■ 181
legend
the section on a map that contains the symbols you need to read the map
Figure 4.2 The Bottom of a Map
Figure 4.3 Map Legend
The map legend identifies the symbols used to depict the prominent natural and man- made objects that exist on the ground. These symbols are not the same on every map, especially foreign maps. Check the legend to avoid making serious mistakes. The legend from the bottom of the map in Figure 4.2 is shown enlarged in Figure 4.3. The sheet name and number provide the title and the reference number for the map. Maps usually take their sheet names from the largest settlement or natural feature on the map. For example, the “Tenino Map” includes the community of Tenino, Wash. The sheet number is in bold print in the upper right and lower left areas of the margin (Figures 4.2 and 4.3). At the lower right margin on the map is a diagram that shows adjoining map sheets. Your map sheet will always be depicted in the center of this diagram. You will learn later in your military studies how to link adjoining map sheets to operational overlays, operation orders, and operation plans.
The scale gives you the ratio of the distance on the map to the distance on the ground. For example, a scale of 1:50,000 (Figure 4.4) indicates that one unit of measure on the map equals one unit of measure on the ground. In other words, one inch on the map equals 50,000 inches on the ground, or approximately 8/10ths of a mile or 1.27 kilometers. The larger the ratio, the less detail can be placed on the map. Likewise, the smaller the ratio, the more detail can be placed on the map. Therefore, a 1:25,000 map will have larger grids, allowing the map-printing agency to place more details onto the map. The contour interval , also found in Figure 4.4, specifies the vertical distance between contour lines. The contour interval for each map will be listed in the lower center of the map margin. Make sure you note whether the interval is in meters or feet.
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scale
the ratio of the map distance to the corresponding distance on the earth’s surface
Figure 4.5 The Three Norths
Figure 4.4 Map Scale, Contour Interval, and Grid Reference Box
Topographic Symbols Military maps show various man-made and natural features using topographic symbols and different colors.
Topographic Symbols
Mapmakers draw maps so you can visualize the landscape with the features in the right place. Your map legend defines the topographic symbols the mapmakers have used to identify the man-made and natural features on the map (Figure 4.7). For example, the topographic symbol used on your map to represent a school would be a small, black rectangle with a pennant drawn on the top. Another example would be a vineyard depicted on your map as a series of close tiny green dots. The legend may show a place of worship as a small rectangle with a cross, an upward arrow, or a crescent drawn on the top. Most maps of the United States will identify churches—no matter the religious denomination—with a cross. This practice will vary in foreign areas. Check the legend to be sure. The legend may show a cemetery as a small rectangle drawn with dotted lines and marked “Cemetery.” In foreign areas, the mapmakers may indicate the religious denomination, if that information is available. Army FM 21-31, Topographic Symbols , describes the symbols, features, and abbreviations approved for military maps. Do not assume that all maps use the same symbols.
Colors
Imagine the difficulty of using a map printed only in black and white. Roads and rivers would look the same—probably with disastrous consequences. As early as the 15th century, mapmakers were coloring their maps. The use of color has become standardized, but check the legend to be sure.
1. Black indicates cultural (man-made) features such as buildings, railroads, and roads
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Figure 4.7 Topographic Symbols
In order to maintain operational security and your night vision, you will use a red-lens flashlight when conducting operations during limited visibility. Older maps printed major roads and built up areas in a red ink that “disappeared” in red- filtered light. Imagine the difficulty of navigating at night when your major roads and built up areas disappeared after you turned on your red-lens flashlight! Mapmakers have recognized the problem and now print military maps with a red-brown ink color that is red-light readable.
topographic symbols
symbols on a map that represent natural and man-made features found on the earth’s surface
The word topography comes from two Greek words: topo , meaning “place or region,” and graphos , meaning “to write.” So a topographic symbol or a topographic map is a detailed and precise description of a place or region.
2. Red and brown combinations identify cultural features (such as major roads), relief features, and contour lines on red-light readable maps 3. Blue identifies water: lakes, swamps, rivers, and coastal waters 4. Green identifies vegetation such as woods, orchards, and vineyards 5. Brown identifies cultivated land on red-light readable maps—on older maps, brown represents relief features and elevation such as contours 6. Red was used on older maps to mark populated areas, main roads, and boundaries 7. Other colors may show special information. Check the legend.
Terrain Features
As you look at the land around you, you will notice different terrain features : the hills, valleys, and other features on the ground. Maps represent these features in specific ways. The Army divides terrain features into three groups: major, minor, and supplementary terrain features. Major terrain features include hills , saddles , valleys , ridges , and depressions. a. A hill is an area of high ground. If you stand on a hilltop, the ground slopes away from you in all directions. A map represents a hill with contour lines forming concentric circles. The inside of the smallest circle is the hilltop (Figure 4.8). b. A saddle is a dip or a low point between two areas of higher ground. If you stand in a saddle, you have high ground in two opposite directions and lower ground in the other two directions. The contour lines on a map representing a saddle are shaped like an hourglass (Figure 4.9). c. A valley is a groove in the land, usually formed by a stream or a river. A valley usually begins with high ground on three sides and has a course of running water through it. If you stand in a valley, you will have higher ground in three directions and lower ground in one direction. Depending on the size of the valley and where you are standing, you may not see the higher ground in the third direction, but the stream or the river will flow from higher to lower ground (Figure 4.10).
Introduction to Map Reading ■ 185
Be aware of how the seasons and climate may affect the presence or depth of intermittent water sources. Maps will display intermittent water sources as blue, but water may not actually be present at the time you are navigating.
Figure 4.8 Hill
terrain features
characteristics of the land, such as hills, ridges, valleys, saddles, depressions, and so forth
Introduction to Map Reading ■ 187
Figure 4.11 Ridge
Figure 4.12 Depression
Minor terrain features include draws, spurs, and cliffs (Figures 4.13 through 4.15).
a. A draw is a small valley. A draw has essentially no level ground and little or no maneuver room. If you are standing in a draw, the ground slopes upward in three directions and downward in the other direction. You could consider a draw to be the initial formation of a valley. A valley will usually have many draws feeding into the valley with streams or intermittent streams feeding into the body of water flowing through the valley. On a map, the contour lines depicting a draw are sharply V-shaped, pointing to higher ground. In most cases, a draw will be situated to the left or right of a spur or lying between two spurs (Figure 4.13). b. A spur is a short ridge. The ground will slope downward in three directions and upward in one direction. On a map, the contour lines depicting a spur are U-shaped pointing away from higher ground. In most cases, a spur will have draws to the left or right, or a spur is situated between two draws (Figure 4.14). c. A cliff is a vertical or near-vertical feature. On a map, the contour lines for cliffs are nearly touching or the contour lines come together to form one contour line depicting the edge of the cliff. Newer maps may also depict a cliff with the
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Figure 4.14 Spur
Figure 4.15 Cliff
Figure 4.13 Draw
2. Three scales—1:100,000; 1:50,000; and 1:25, 3. An inner scale of 360 degrees, which you use to plot azimuths (You’ll learn more about azimuths in the next section.) 4. An outer, mils scale. (There are 6400 mils in a circle. You’ll learn to use this scale for indirect fire.)
Using Four-Digit Grid Coordinates to Determine a Location
Earlier in this section you learned that mapmakers break down the earth’s surface into 60 grid zone designators. The grid zone designator for your Tenino map, for example, is 10T. Each of these grid zone designators covers very large areas of the earth’s surface. Because grid zones are not manageable in size when navigating, the mapmakers further break down each grid zone into 100,000-meter squares to make the grid zones more manageable. This means that the distance between each grid line is 100,000 meters. For example, the area on your Tenino map covers portions of two 100,000-meter squares, and their identification is EH and EG. Unless you are flying, you will never need to navigate over an area as large as a 100,000-meter square. So mapmakers break down the earth’s surface within the 100,000-meter squares into 10,000-meter squares (Figure 4.18) and then into even smaller, 1,000-meter squares (Figure 4.19) and number them beginning with 00 and ending in 99 (see Figure 4.4). Between each number, 01 and 02 for example, the distance is 1,000 meters. Now imagine you are behind enemy lines and you are in satellite radio contact with your rescue aircraft, which is in another part of the world. You cannot simply give your
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Figure 4.17 Army Protractor (GTA 5-2-12, 1981)
Introduction to Map Reading ■ 191
Figure 4.18 10,000-Meter Grid Square
Figure 4.19 Four-Digit or 1,000-Meter Grid Square
have an even set of numbers. In a four-digit grid, the first half of the grid coordinate numbers represents the horizontal, “left-to-right” or “easting” reading. The second half of the grid coordinate numbers represents the vertical,“bottom-to-top” or “northing” reading. For example, grid coordinate 16SGL0182 in Figure 4.19 would identify all of the area within the grid square to the right of line 01 and above line 82. The critical rule is to read right and then up. Notice how the example reads right and then up : Grid square 0182 was to the right of line 01 and above— up from—line 82.
Using Six-Digit Grid Coordinates to Determine a Location
Submitting a four-digit grid location may be acceptable for large-scale operations or large- scale units. For example, a one-grid-square location might be sufficient for identifying the location of a brigade combat team forward operating base or a zone reconnaissance for a company-sized element. There are other situations, however, where your grid locations must be narrowed down in order to be more accurate than a 1,000-meter square For situations in which you need to be within a 100-meter square—such as calling for indirect fire or close air support, or calling for an emergency resupply or medical evacuation— you will need to know how to determine and plot six-digit grid coordinates. Think back to the earlier search-and-rescue scenario. Imagine you are hunkered down in hiding because enemy forces are actively searching for you. It is crucial to your survival that your rescuers find you quickly. Rather than have them search an entire grid square for you, you radio your rescuers, “Rescue 6, this is Lost Sheep 3, I am at grid Sixteen-Sierra, Golf Lima, Zero-One-Two, Eight-Two-Eight (Figures 4.20, 4.21, and 4.22). Rather than searching for an hour, your rescuers hover within 100 meters of your location within a matter of minutes.
Introduction to Map Reading ■ 193
Figure 4.20 Six-Digit or 100-Meter Grid Square
Follow these five steps to identify a more specific location:
1. Make sure you are using the appropriate scale (check the scale in the map’s marginal information) and make sure the scale is right side up 2. Place the protractor scale with the zero-zero point at the lower left corner of the appropriate grid square 3. Keep the horizontal line of the protractor’s scale directly on top of the horizontal, left-to-right, or “easting” grid line, and slide the protractor—and its scale—to the right until the left vertical line of the grid square touches the point on the protractor scale for the coordinate you want 4. Read up the vertical scale until you reach the coordinate you want 5. Mark the location.
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Figure 4.21 Plotting a Specific Point
Figure 4.22 Read Right, Then Up: Six-Digit Grid Coordinate 16SGL
CONCLUSION
MAJ Wright, his driver, and an NCO wound up “out in the boonies” because none of them had looked at a map before leaving for the airport. Knowing how to read a map and plot coordinates are essential military skills. In this section, you learned how to determine and plot a grid coordinate with 100-meter square accuracy. In later sections, you will learn how to plot and determine grid coordinates within a 10-meter square by using eight- and 10-digit grid coordinates. During any mission you must always know where you are and where you are going. If you are to be a credible leader, your Soldiers must be confident that you are proficient in map reading and land navigation. Take the time now to gain and polish your map- reading skills. Not only are they important to your Army career—they can save your life or your Soldiers’ lives in combat.
Learning Assessment
1. Describe and explain in your own words the five major terrain features of hill, **valley, saddle, ridge, and depression.
- Explain the difference between a draw and a valley; and between a spur and** **a ridge.
- Define man-made and natural objects depicted on a military map by** **topographical symbols.
- Which is more precise—a four-digit or six-digit grid location?
- Explain how to determine a four-digit grid location of an object on a** **military map.
- Explain how to determine a six-digit grid location of an object on a** **military map.
- Describe how to identify a four-digit grid coordinate on a military map.
- Describe how to identify a six-digit grid coordinate on a military map.**
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Key Words
legend
scale
declination
true north
magnetic north
grid north
G-M angle
topographic symbols
terrain features
grid coordinates
References
Department of the Army, XVIII Airborne Corps. (6 April 1990). Joint Task Force South in Operation Just Cause. Oral History Interview JCIT 046. Fort Bragg, NC. Retrieved 8 July 2005 from http://www.army.mil/cmh-pg/documents/panama/jcit/JCIT46.htm
Field Manual 1-02, Operational Terms and Graphics. September 2004.
Field Manual 3-25.26, Map Reading and Land Navigation. 18 January 2005.
Field Manual 21-31, Topographic Symbols. Change 1. December 1968.
Introduction to Map Reading ■ 197
