Map Reading Essay Sample
- Word count: 2188
- Category: maps
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Map Reading Essay Sample
Cadets and Cadettes, good morning/afternoon. Our new subject matter today is considered as one of the mandatory subject of the AFP in which every individual soldier must equip himself/herself to effectively and successfully perform his/her given mission. A military man, just like any other craftsman, is provided with various tools in order to accomplish his task. He is provided with weapons, transportation, communication facilities, medication and other kinds of equipment. All as important as the others. One kind of equipment which is used by military men from the lowest soldier in the ranks to the topmost commander is the map. A map plays a vital role in a military man’s life. He uses it as a guide to his objective; it gives him information about the characteristics of the ground in his area of operations and other information essential to the planning and conduct of an operation. Often times, the only source of information is a map. We can therefore see how important a map is to everyone in the military service. However, having a map is not enough. In order that it can be of use, a soldier should be able to read or interpret what is shown in the map.
What is a map?
A map is a systematic representation of all or a part of the earth’s surface, drawn or formed to scale on a plane as seen from above. Marine (Hydrographic) and air (Aeronautical) maps are generally called charts. In the broadest sense the words “maps” or “chart” can be used for any conventionalized representation of spatial phenomena, such as the heavens or the brain. Manmade and natural features are depicted by symbols, lines, colors and forms.
Why are maps important?
First of all, all flat maps have some distortion, since it is impossible to represent the curving figure of the earth on a plane without deformation. Nevertheless, maps possess positive qualities that makes them more than poor substitute for the globe. Example of this is the plotting of directions is more easily accomplished on maps than in globes. In fact nowadays globes are rarely used for navigation. There would be little advantage in having a curving surface for regions of sub-continental or smaller size and so maps, rather than segments of the globe are commonly used for representing such areas. Furthermore it is easier to make, transport, and store maps than globes, and when used correctly a map can give accurate information on such factors as distances, locations, heights, best routes, key terrain features, concealment and cover.
Security of Maps:
Should a map fall into unauthorized hands, it could give an indication of our future plans or areas of interest to the enemies. MAPS MUST NOT FALL INTO UNAUTHORIZED HANDS.
Care of Maps:
a. One of the first considerations in the care of maps is the proper folding of the map itself, to make them small enough to be carried easily and still be available for use without having to unfold them entirely. b. Most maps are printed on paper and require protection from water, mud and tearing, whenever possible, carry a map in a water proof pocket. c. If it is necessary to mark a map, use light lines so that they may be erased easily without smearing or smudging or leaving marks that they may later cause confusion.
BASIC FEATURES OF MAPS
An amazing variety of maps exists, but there are certain basic features common to most of them. Even outline maps, which are designed to enable the student to add such information as he chooses, usually possess a grid, scale, and base data or marginal information. In addition to these features maps also have, characteristically, various conventional symbols (known collectively as “map data”), a legend or key, and lettering on the map itself.
In cartography the term “grid” (or “graticule”) means the network of lines of latitude and longitude used on a map or globe. The term “grid” is also used for a reference system consisting typically, of evenly spaced lines crossing each other at 90 angle (a Cartesian grid). Such reference systems, which are often used in street maps and for military purposes may or may not have a direct relationship to latitude and longitude.
Methods on Reading the Map
1. Grid Squaring – 4 digits
2. Grid Coordinate (nearest 100 meters) – 6 digits
3. Grid Coordinate (nearest 10 meters) – 8 digits
– is expressed as a fraction and gives the ratio of map distance to ground distance. 1. Small Scale – Maps at scale of 1:600,000 and smaller are used for general planning and for strategic studies at the high echelons. 2. Medium Scale – Maps at scales larger than 1:600,000 but smaller than 1:75,000 are used for planning operations including the movement and concentration of troops and supplies. 3. Large Scale – Maps at scales of 1:75,000 and larger are used to meet the tactical, technical and administrative needs of field units.
On most military maps there is another method of determining ground distance. It is by means of the GRAPHIC SCALES. A graphic scale is a RULER printed on the map on which distances on the map may be measured as actual ground distance.
a.To determine a straight line ground distance between two points on the map. b.To measure distance along a winding road, stream, or any other curved line, the straight edge of a piece of paper is used again.
Types of Maps:
1. Planimetric Map
2. Topographic Map
3. Plastic Relief Map
5. Plastic Relief Photomap
7. Military City Map
8. Special Maps
9. Terrain Model
Map reading, especially in the field, is facilitated if the map is placed in correct orientation, that is, with the features in the same direction as they occur on the earth. On the map, direction is sometimes indicated by a compass rose and sometimes by a north-pointing arrow.
Magnetic or Lensatic Compass
– a military instrument used to measure angles and directions in the field
ORIENTATION OF A MAP
BY THE USE OF A COMPASS (Magnetic or Lensatic Compass)
Before a map can be used, it must be oriented. A map is oriented when, in a horizontal position, “its north points north” all map lines are then parallel to their corresponding lines on the ground. A simple way to orient a map is with a compass. Find the magnetic north line, open the compass and align the compass sighting wire over the magnetic north line. Rotate the map and compass until the needle, sighting wire and the magnetic declination arrow on the map are all pointing in the same direction.
BY AREA INSPECTION
When a compass is not available, map orientation requires a careful examination of the map and the ground to find linear features common to both, such as roads, railroads, fence lines, power lines, etc. By aligning the feature on the ground, the map is oriented.
ORIENTATION OF THE MAP DURING DAYTIME WITHOUT A COMPASS
a) WESTING & EASTING METHOD
b) SHADOW METHOD
c) SHADOWTIP METHOD
d) CLOCK METHOD
ORIENTATION OF THE MAP DURING NIGHTTIME WITHOUT A COMPASS
a) BIG DIPPER – finding direction by the NORTH STAR
b) SOUTHERN CROSS STAR – finding direction in the southern hemisphere by the southern cross
METHODS OF LOCATING POINTS
1. Intersection – Location of an unknown point by successively occupying two known positions and sighting on the unknown point – “ASĀ SILA?” Procedure: Map and compass method
1. Orient the map using the compass.
2. Locate and mark your position on the map.
3. Sight on the unknown position. Draw a line on the map from your position toward the unknown point. 4. Move to another position and locate this position on the map. 5. Sight on the unknown position. Draw a second line on the map from your position to the unknown point. 6. Where the two lines cross is the location of the feature.
2. Resection – Location of the user’s position by sighting on 2 known features is called resection. “ASĀ AKO?” Procedure:
1. Orient the map and select two outstanding features on the ground which can be identified on the map. 2. Place the straight edge on a line between the visible point on the ground and its plotted position on the map, draw a line. 3. Extend the line back in your direction.
4. Repeat #2 and #3 using the second feature and its plotted position. 5. Where the two lines cross is your position.
3. Polar Coordinates – A point on the map may be determined or plotted from a known point by giving a direction and a distance along that direction line. The reference direction is normally expressed as an azimuth and a distance in any convenient unit of measurement such as meters or yards. Polar coordinates are especially useful in the field because magnetic azimuth can be determined from the compass and the distance can be estimated.
4. Modified Resection – A point on the map may be determined or plotted by giving a direction and a distance from the reference outstanding feature. 4.MARGINAL INFORMATION (Base Data and Symbols)
The outer edges of a map contain information, which is used to interpret the map. All maps are not the same so it is necessary, every time a different map is used, to examine carefully the marginal information.
1. Sheet Name – is found in two places; the center of the upper margin and the right side of the lower margin. Generally, a map is named after its outstanding cultural or geographic feature. Whenever possible, the name of the largest city on the map is used. 2. Sheet Number – is found in the upper right margin and is used as a reference number assigned to each map sheet. 3. Series Name and Scale – is found in the upper left margin. A map series usually comprises a group of similar maps at the same scale and on the same sheet lines and format, designed to cover a particular geographic area. 4. Series Number – appears in the upper right margin and in the lower left margin. 5. Edition Number – is found in the upper margin and in the lower left margin. It represents the age of the map in relation to other editions of the same map. 6. Bar Scales – are located in the center of the lower margin. They are rulers used for the determination of the ground distance. 7. Credit Note – is in the lower left margin. It lists the producer and reference method of compilation. 8. Index to Adjoining Sheets – appears in the lower margin. It identifies the map sheets surrounding the map.
9. Index Boundaries – appears in the lower or right margin. It shows the boundaries which occur within the map area. 10. Projection Note – is located in the center of the lower margin. 11. Grid Note – located in the center of the lower margin. It gives information pertaining to the grid system used. 12. Grid Reference Box – located in the lower margin. It contains information for identifying the grid zone. 13. Vertical Datum Note – located in the center of the lower margin. It designates the basis for all-vertical control stations and elevations appearing on the map. 14. Horizontal Datum Note – located in the center of the lower margin. It indicates the basis for all-horizontal control stations and elevations appearing on the map. 15. Legend – is located in the lower left margin. It illustrates and identifies the topographic symbols used to depict the more prominent features on the map.
16. Declaration Diagram – is located in the lower margin and indicates the angular relationships of true North, grid north and magnetic north. 17. User’s Note – is located in the center of the lower margin. It requests cooperation in correcting errors or omissions on the map. 18. Unit Imprint – is located in the lower right margin. It identifies the agency which printed the map and the date of printing. 19. Contour Interval – appears in the center of the lower margin. It states the vertical distance between adjacent contour lines on the map. 20. Special Notes and Scales – (not included in the Leavenworth map). Under certain conditions, special notes or scales may be added to the marginal information to aid the map user. TOPOGRAPHIC MAP SYMBOLS AND COLORS
– are used to represent the natural and manmade features of the earth.
1. BLACK – all manmade features
2. BLUE – water features such as lakes, rivers and swamps
3. GREEN – vegetation such as woods, orchards and vineyards
4. RED – main roads built up areas and special features
MILITARY SYMBOLS AND COLORS
– are used to show the identity, strength, locations, and movements of its troops’ activities and installations. 1. BLUE – friendly forces
2. RED – enemy forces
3. GREEN – engineer obstacles; both friendly and enemy
4. YELLOW – contaminated areas; both friendly and enemy