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Map Reading

Map Reading. For use with the Tenino map. Basic Map Skills. Identify Map Colors Identify Map Symbols Identify Marginal Information Identify Terrain Features. Map Colors. Black - Indicates cultural (man-made) features such as buildings and roads, surveyed spot elevations, and all labels.

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Map Reading

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  1. Map Reading For use with the Tenino map

  2. Basic Map Skills • Identify Map Colors • Identify Map Symbols • Identify Marginal Information • Identify Terrain Features

  3. Map Colors • Black - Indicates cultural (man-made) features such as buildings and roads, surveyed spot elevations, and all labels. • Red - Classifies cultural features, such as populated areas, main roads, and boundaries, on older maps • Red-Brown - Combined to identify cultural features, all relief features, non-surveyed spot elevations, and elevation, such as contour lines on red-light readable maps.

  4. Map Colors • 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. • Other - Occasionally other colors may be used to show special information. These are indicated in the marginal information as a rule.

  5. Identify Map Symbols Refer to Legend

  6. Marginal Information • Name of map sheet: named after largest city or natural feature • Series name: name of major political subdivision ie: state • Scale: ratio of map distance to corresponding distance on Earth • Series number: sequence reference • Edition number: newest edition will have highest number • Sheet number: reference to link adjoining maps together • Legend: annotates what map symbols represent • Bar scale: rulers to convert map distance to ground distance • Declination diagram: angular relationships of true, grid and magnetic north; map/compass azimuth conversion • Grid reference box: Grid zone identification • Adjoining Sheets Diagram: relation of sheet to other sheets

  7. Marginal Info Map Location 6 5 2 1 3 4 9 11 7 10 8 2 5 6 1 1. Sheet Name: Tenino 2. Sheet Number: 1477 IV 3. Series Name: Washington 4. Scale: 1:50,000 5. Series Number: V791 6. Edition Number: 7-DMATC 7. Legend 8. Grid Reference Box. 9. Bar Scales 10. Declination Diagram 11. Adjoining Sheets Diagram

  8. Check On Learning 1. What are the six colors used on a military map and what do they represent? 2. What portion of a map explains the symbols and features used, and where can you find it? 3. What are the Map Series Name, Scale, and Series Number of your Tenino Map? 4. Where is the declination diagram and what does it tell you? 5. What is the adjoining sheet number directly south of the Tenino Map Sheet?

  9. Terrain Features

  10. Terrain Features - Major • Hill • Valley • Ridge • Saddle • Depression Need help remembering? Hidden Valley Ranch Salad Dressing

  11. HILL A hill is an area of high ground. From a hilltop, the ground slopes down in all directions. A map depicts a hill by showing contour lines forming concentric circles (circles having a common center). The inside of the smallest closed circle is the hilltop

  12. VALLEY A valley is a stretched out groove in the land, usually formed by streams or major rivers. If standing in a valley, three directions offer high ground, while the fourth direction offers low ground. The contour lines forming a valley are either U-shaped or V-shaped. The closed end of the contour line (U or V) always points upstream or toward higher ground.

  13. RIDGE A ridge is a sloping line of high ground. If you are standing on the centerline of a ridge, you will normally have low ground in three directions and high ground in one direction with varying degrees of slope. If you cross a ridge at right angles, you will climb steeply to the crest and then descend steeply to the base. Contour lines forming a ridge tend to be U-shaped or V-shaped. The closed end of the contour line points away from high ground.

  14. SADDLE A saddle is a dip or low point between two areas of higher ground. A saddle is not necessarily the lower ground between two hilltops; it may be simply a dip or break along a level ridge crest. If you are in a saddle, there is high ground in two opposite directions and lower ground in the other two opposite directions.

  15. DEPRESSION A depression is a low point in the ground or a sinkhole. It could bedescribed as an area of low ground surrounded by higher ground in all directions, or simply a hole in the ground. Usually only depressions that are equal to or greater than the contour interval will be shown. On maps, depressions are represented by closed contour lines that have tick marks pointing toward low ground.

  16. Terrain Features - Minor • Draw • Spur Terrain Features - Supplementary • Cliff • Cut • Fill

  17. DRAW A draw is a stream course that is less developed than a valley. In a draw, there is essentially no level ground and, therefore, little or no maneuver room within its confines. If you are standing in a draw, the ground slopes upward in three directions and downward in the other direction. A draw could be considered as the initial formation of a valley.

  18. SPUR A spur is a short, continuous sloping line of higher ground, normally jutting out from the side of a ridge. A spur is often formed by two roughly parallel streams cutting draws down the side of a ridge. The ground will slope down in three directions and up in one. Contour lines on a map depict a spur with the U or V pointing away from high ground.

  19. CLIFF A cliff is a vertical or near vertical feature; it is an abrupt change of the land. When a slope is so steep that the contour lines converge into one “carrying” contour of contours, this last contour line has tick marks pointing toward low ground. Cliffs are also shown by contour lines very close together and, in some instances, touching each other.

  20. CUT A cut is a man-made feature resulting from cutting through raised ground, usually to form a level bed for a road or railroad track. Cuts are shown on a map when they are at least 10 feet high, and they are drawn with a contour line along the cut line. This contour line extends the length of the cut and has tick marks that extend from the cut line to the roadbed, if the map scale permits this level of detail.

  21. FILL A fill is a man-made feature resulting from filling a low area, usually to form a level bed for a road or railroad track. Fills are shown on a map when they are at least 10 feet high, and they are drawn with a contour line along the fill line. This contour line extends the length of the filled area and has tick marks that point toward lower ground. If the map scale permits, the length of the fill tick marks are drawn to scale.

  22. PRACTICAL EXERCISE 1. Hill 2. Valley 3. Ridge 4. Saddle 5. Depression ANSWERS: 6. Draw 7. Spur 8. Cliff 9. Cut 10. Fill

  23. Basic Map Skills • Identify Grid • Determine Elevation • Determine Azimuth / Back Azimuth • Grid vs. Magnetic Azimuth • Determine Distance

  24. Identify a Grid

  25. Grid Zone Identification • 4-Digit Coordinate: within 1000 meters • 6-Digit Coordinate: within 100 meters • 8-Digit Coordinate: within 10 meters • *The more digits in a grid coordinate, the closer the location.

  26. 4-Digit Grid • Read Right then Up • Bottom left corner identifies first two digits • Right:11 Up: 81 ex. 1181e • Add proper grid zone designator to front • ex. AB1181

  27. 6-Digit Grid • Read Right then Up • Bottom left corner identifies first two digits 1181e • Use coordinate scale to identify last digit • ex. 115813 • Add proper grid zone designator to front ex: AB115813

  28. 8-Digit Grid 50m tick marks • If point is between 2-100 meter tick marks use the • 50 meter tick marks to help estimate

  29. 8-Digit Grid 2 3 5 6 7 8 9 1 2 3 4 82 9 8 7 6 5 4 AB 11578136 3 2 1 81 4 5 6 7 8 9 12 • Read Right then Up • Bottom left corner identifies first two digits 1181e • Use coordinate scale to identify last two digits ex: 11578136 • Add proper grid zone designator to front ex: AB 11578136

  30. PRACTICAL EXERCISE 1. What is the name of the mountain in grid EG1486? ANSWER: Northcraft Mountain 2. What’s the name of the lake in grid EH0103? ANSWER: Black Lake 3. What number benchmark is in grid EG0589? ANSWER: BM 86 4. What is the 6-digit coordinate of the TV relay tower found at EG1287? ANSWER: EG 126877 5. What is the 6-digit coordinate of the lake found at EG0998? ANSWER: EG 095984 6. What is the 8-digit coordinate of the Deschutes Fire Tower found at EG1795? ANSWER: EG 17679514 7. What is the 8-digit coordinate of the coal mine found at EG1582? ANSWER: EG 15848215 8. What is the 8-digit coordinate of the hilltop found at EH0302? ANSWER: EH 03390235

  31. Determine Elevation

  32. Determine Elevation • Locate point on the map • Determine contour interval of map • Locate index contour line nearest point • Count number of contour lines up or down that must be crossed to get to point • Points at top of hill add half the contour interval • Points at bottom of depression subtract half the contour interval

  33. Determine Azimuth

  34. Determine Azimuth Azimuth: a horizontal angle measured clockwise from a north base line. This north base line could be true north, magnetic north, or grid north. The azimuth is the most common military method to express direction. • Plot location of two points. • Use straight edge to draw line between both points (line must be long enough to cross scale on protractor) • Place the index of the protractor at the point where the drawn line crosses a vertical (north-south) grid line. • Keeping the index at this point, align the 0-to-180 degree line of the protractor on the vertical grid line. • Read the value of the angle from the scale; this is the grid azimuth from point A to point B.

  35. A 104° B When measuring azimuths on a map, remember that you are measuring from a starting point to an ending point. If a mistake is made and the reading is taken from the ending point, the grid azimuth will be opposite, thus causing the user to go in the wrong direction.

  36. Back Azimuth • A back azimuth is the opposite direction of an azimuth. It is comparable to doing an "about face." • Back Azimuth - azimuth taken from a distant point toward your location • Used in Resection • Numbers less than 180°: add 180° Ex: azimuth = 145°, resection = 145°+180° = 325° • Numbers greater than 180°: subtract 180° Ex: azimuth = 270°, resection = 270°-180° = 90°

  37. PRACTICAL EXERCISE 1. What is the grid azimuth from the TV relay tower in EG1287 to the water tower in EG0985? What is the back azimuth? ANSWER: azimuth = 233° back azimuth = 53° 2. What is the grid azimuth from the bridge in EG0292 to the mine pit in EG0694? What is the back azimuth?ANSWER: azimuth = 68° back azimuth = 248° 3. What is the grid azimuth from the Deschutes Fire Tower in EG1795 to BM 88 in EG1798? What is the back azimuth?ANSWER: azimuth = 6° back azimuth = 186° 4. What is the grid azimuth from the BM 65 in EH0900 to the bridge in EG1196? What is the back azimuth?ANSWER: azimuth = 161° back azimuth = 341°

  38. Grid vs. Magnetic Azimuth

  39. The Three Norths • True North: A line from any point on the earth's surface to the north pole. All lines of longitude are true north lines. • Magnetic North: The direction to the north magnetic pole, as indicated by the north-seeking needle of a magnetic instrument. ie: a compass • Grid North: The north that is established by using the vertical grid lines on the map.

  40. Grid-Magnetic Angle: The G-M angle value is the angular size that exists between grid north and magnetic north. Azimuths translated between map and ground will be in error by the size of the declination angle if not adjusted for it.

  41. Converting Grid/Magnetic Azimuths Since the location of magnetic north does not correspond exactly with the grid-north lines on the maps, a conversion from magnetic to grid or vice versa is needed. Grid to Magnetic azimuth: • East G-M angle: subtract • Ex: GM angle: 21°, grid azimuth: 360° magnetic azimuth: 360°-21°=339° Magnetic to Grid azimuth: • East G-M angle: add • Ex: GM angle: 21°, grid azimuth: 360° magnetic azimuth: 360°+21°=21° • Refer to the conversion notes with Declination Diagram. 21° Easterly Declination *There are no negative azimuths on the azimuth circle; will be between 0° and 360° ex: -30° = 330°, 380°= 220°

  42. Converting Grid/Magnetic Azimuths Since the location of magnetic north does not correspond exactly with the grid-north lines on the maps, a conversion from magnetic to grid or vice versa is needed. Grid to Magnetic azimuth: • West G-M angle: add • Ex: GM angle: 30°, grid azimuth: 140° magnetic azimuth: 140°+30°=170° Magnetic to Grid azimuth: • West G-M angle: subtract • Ex: GM angle: 30°, grid azimuth: 140° magnetic azimuth: 140°-30°=110° • Refer to the conversion notes with Declination Diagram. 30° Westerly Declination *There are no negative azimuths on the azimuth circle; will be between 0° and 360° ex: -30° = 330°, 380°= 220°

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