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Presentation Overview • Map Basics • Definition • Marginal Information • Map Colors • Grid Lines • 8-Digit Grid Coordinate • Locating • Plotting • Determining Distance • Straight-Line Distance • Irregular Distance • Contour Lines • Basics • Determining Elevation • Relief & Terrain Features • Slope Types • Hill, Draw, Ridge, Finger, Saddle, Cliff, Depression, Cuts, Fills • GM Angle, Azimuth, and North • Quiz • Next Time: Land Navigation II • Lensatic Compass • Orienting a Map • Determine an Azimuth • Follow an Azimuth • Questions?
Presentation Overview • Map Basics • Definition • Marginal Information • Map Colors • Grid Lines • 8-Digit Grid Coordinate • Locating • Plotting • Determining Distance • Straight-Line Distance • Irregular Distance • Contour Lines • Basics • Determining Elevation • Relief & Terrain Features • Slope Types • Hill, Draw, Ridge, Finger, Saddle, Cliff, Depression, Cuts, Fills • GM Angle, Azimuth, and North • Questions? • Quiz • Next Time: Land Navigation II • Lensatic Compass • Orienting a Map • Determine an Azimuth • Follow an Azimuth
Map Basics • Definition: A map is a mathematically determined representation of the Earth’s surface systematically plotted to scale upon a plane surface.
Map Basics: Marginal Information • Information that helps us read & interpret a map • Graphic (bar) scales are rulers used to convert horizontal map distance to ground distance • Right of 0 is primary scale • Left of 0 is extension scale
Map Basics: Marginal Information (cont.) • Legend • Illustrates and identifies the topographic symbols used to depict prominent features on the map. Symbols on one map may not mean the same things on another map
Map Basics: Legend Includes all kinds of information, from the size/condition of roads to mines, chapels and other man-made features. Note: See Legend on back of Handout Map
Map Basics: Marginal Information (cont.) • Map Scales • Representative Fraction is the scale of the map which expresses the ratio of horizontal distance on the map to the corresponding horizontal distance on the ground: • 1:25,000 SCALE. • 1:50,000 SCALE • 1:100,000 SCALE • 1:250,000 SCALE • The smaller the number on the bottom, the larger the scale of the map
Map Basics: Map Scales (cont.) • Small scale maps - Maps that have a scale of 1:1,000,000 and smaller. These maps are used for general planning and for strategically studies at the higher echelons. • The standardsmall scale map is 1:1,000,000
Map Basics: Map Scales (cont.) • Medium scale maps - Are maps of scales that are larger than 1:1,000,000 but smaller than 1:75,000. • These maps are used for planning operations, including the movement and concentration of marines and supplies. • The standard medium scale map is 1:250,000.
Map Basics: Map Scales (cont.) • Large scale maps - Are maps that are 1:75,000 and larger. • They are used to meet tactical, technical, and administrative needs of the field units. • The standard Large scale map is 1:50,000.
Map Basics: Colors • Black: Man-made objects • Buildings, some roads, cultural, etc. • Red: Main roads • Also some special features • Blue: Water features • Lakes, rivers, ponds, ocean, etc. • Green: Vegetation • Forrest, orchard, etc. • Brown: Relief features • Contour lines.
Map Basics: Grid Lines • A series of straight lines intersecting at right angles forming squares • Horizontal grid lines run grid west to grid east • Vertical grid lines run grid south to grid north • On most military maps a grid square is 1000X1000 meters • Basic Rule: Read right on the vertical lines, then up on the horizontal grid lines
Presentation Overview • Map Basics • Definition • Marginal Information • Map Colors • Grid Lines • 8-Digit Grid Coordinate • Locating • Plotting • Determining Distance • Straight-Line Distance • Irregular Distance • Contour Lines • Basics • Determining Elevation • Relief & Terrain Features • Slope Types • Hill, Draw, Ridge, Finger, Saddle, Cliff, Depression, Cuts, Fills • GM Angle, Azimuth Conversion, and Norths • Quiz • Next Time: Land Navigation II • Lensatic Compass • Orienting a Map • Determine an Azimuth • Follow an Azimuth • Questions?
8-Digit Grid Coordinate • A grid square’s coordinates are found by combining the values of the vertical and horizontal grid lines that intersect at the lower left hand corner of the grid. • Always, read right, then up • A 4-digit grid coordinate locates a point to within 1000 square meters.
Coordinate Scale • Divides the grid square more accurately and consistently that estimation • 1:25000 coordinate scale divides the 1000 square meter block into ten 100 meter divisions, the ten divisions are further divided into 20 meter blocks
Finding the Grid Coordinate of a Point • First determine the grid square the point is in. This gives 4 digits: 12xx56xx. • Next, using correct scale on protractor, align the bottom right corner of the protractor scale to the bottom right corner of the grid square. • Slide the protractor to the left until the right edge of the scale intersects the point. • Read off the horizontal and vertical position: • 12345678
23 22 21 20 19 18 46 Grid: 49551885 Gives second two longitude (horizontal) coordinates: 85 Gives second two latitude (vertical) coordinates: 55 47 48 49 50 51 52 53 54
Plotting a Grid Coordinate • Grid Coordinate 12345678 • Divide into horizontal and vertical measurements: 1234 5678 • Next locate primary coordinates that give grid square: • 12345678: 12 and 56 are primary coordinates that provide the grid square • The 34 and 78 and determined by using the tick marks on the protractor
Presentation Overview • Map Basics • Definition • Marginal Information • Map Colors • Grid Lines • 8-Digit Grid Coordinate • Locating • Plotting • Determining Distance • Straight-Line Distance • Irregular Distance • Contour Lines • Basics • Determining Elevation • Relief & Terrain Features • Slope Types • Hill, Draw, Ridge, Finger, Saddle, Cliff, Depression, Cuts, Fills • GM Angle, Azimuth Conversion, and Norths • Quiz • Next Time: Land Navigation II • Lensatic Compass • Orienting a Map • Determine an Azimuth • Follow an Azimuth • Questions?
Determining Distance: Straight Line • The shortest distance between the two points • Lay a straight piece of paper between two points • Make two tickmarks on the paper corresponding to the centers of the two points • Move the paper down to the graphic scale • Make sure you use meters
Determining Distance: Irregular Line • Used for winding roads, curved lines • Lay paper down so one edge is on the start point, make a tick mark at the start point and another where the edge of the paper leaves the center of the curve/line • Pivot the paper with the pencil on the second point • to align the paper with the center of the curve, make another tick mark when the paper leaves the center of the curve • Continue until measurement is completed • Transfer paper to the graphic scale to compute the distance
Presentation Overview • Map Basics • Definition • Marginal Information • Map Colors • Grid Lines • 8-Digit Grid Coordinate • Locating • Plotting • Determining Distance • Straight-Line Distance • Irregular Distance • Contour Lines • Basics • Determining Elevation • Relief & Terrain Features • Slope Types • Hill, Draw, Ridge, Finger, Saddle, Cliff, Depression, Cuts, Fills • GM Angle, Azimuth Conversion, and Norths • Quiz • Next Time: Land Navigation II • Lensatic Compass • Orienting a Map • Determine an Azimuth • Follow an Azimuth • Questions?
Contour Lines: Basics • A contour line is a line drawn on a map representing an imaginary line on the ground along which all points are the same elevation • Indicates the vertical distance above or below a base plane • The vertical distance between two lines is the contour interval, found in the marginal data • Every fifth line is an index contour, it is shaded thicker and heavier • The lines in between are intermediate contours • Every line counted represents a change in elevation equal to the contour interval
10 2 1 x358 3 350 4 5 350 6 9 300 8 7 Contour Lines: Basics Supplementary Contour Line Intermediate Contour Line Index Contour Line
Contour Lines: Determining Elevation • If a point is on a line its elevation is that of the contour line • For the estimation of elevation of a point between contour intervals is equal to 1/2 change in contour interval • A hilltop is 1/2 plus the elevation of the contour line around the hilltop unless otherwise stated • A depression is equal to the contour line around the depression minus 1/2 the contour interval
Presentation Overview • Map Basics • Definition • Marginal Information • Map Colors • Grid Lines • 8-Digit Grid Coordinate • Locating • Plotting • Determining Distance • Straight-Line Distance • Irregular Distance • Contour Lines • Basics • Determining Elevation • Relief & Terrain Features • Slope Types • Hill, Draw, Ridge, Finger, Saddle, Cliff, Depression, Cuts, Fills • GM Angle, Azimuth Conversion, and Norths • Quiz • Next Time: Land Navigation II • Lensatic Compass • Orienting a Map • Determine an Azimuth • Follow an Azimuth • Questions?
Relief & Terrain Features:Slopes • Evenly spaced and wide apart contour lines indicate a uniform gentle slope • Evenly spaced and close together contour lines indicate a uniform steep slope • Lines closely spaced at the top and widely spaced at the bottom is a concave slope • Lines widely spaced at the top and closely spaced at the bottom indicates a convex slope
Relief & Terrain Features:Terrain Features • Hill: Indicated by closed loop. The ground slopes down in all directions • Draws: Less developed stream courses • ground slopes upward in three sides and down one side. • V points to higher elevation
Relief & Terrain Features:Terrain Features • Ridge: A line of high ground with normally minor variations along its crest • Not simply a line of hills • The points of the ridge are higher than the ground around it • Finger: A continous line of sloping ground usually jutting from the side of a ridge
Relief & Terrain Features:Terrain Features • Saddle: A dip or low point along the crest of the ridge • Cliff: A vertical or near vertical slope. So steep it is indicated by tick-marks pointing to lower elevation
Relief & Terrain Features:Terrain Features • Depression: A low-point or sinkhole surrounded on all sides by higher ground • Tick marks point to lower ground • Each ticked contour circles represents a change in elevation equal to one contour interval • Valley: A stretched-out groove in the land • Usually formed by streams or rivers
Presentation Overview • Map Basics • Definition • Marginal Information • Map Colors • Grid Lines • 8-Digit Grid Coordinate • Locating • Plotting • Determining Distance • Straight-Line Distance • Irregular Distance • Contour Lines • Basics • Determining Elevation • Relief & Terrain Features • Slope Types • Hill, Draw, Ridge, Finger, Saddle, Cliff, Depression, Cuts, Fills • GM Angle, Azimuth Conversion, and Norths • Quiz • Next Time: Land Navigation II • Lensatic Compass • Orienting a Map • Determine an Azimuth • Follow an Azimuth • Questions?
GM Angle, Azimuth Conversion, and North • Three Norths • Grid-The vertical lines on the map • Magnetic-Magnetic North in Hudson Bay • True-North Pole • Declination Diagram shows the relationships between the three norths • Magnetic and Grid North are used to determine GM (Grid-Magnetic) Angle
Azimuths • An azimuth is a direction • Defined as a horizontal angle measured clockwise from a baseline • There are two types dealt with • magnetic azimuths measured with true north as its base • grid azimuths measures with grid north as base
Measuring Azimuths • Plot two coordinates on the map • connect them with a straight line • Place the index point pf the protractor on the point the azimuth its to be measured from • Ensure the protractor grid lines are parallel to N-S gridlines on a map • Where the line crosses the protactor indicates azimuth
Converting Azimuths • Use the GM angle to convert grid to magnetic and magnetic to grid • When going from Grid to Magnetic • LARS ( Left Add/ Right Subtract) • This will almost always be the case • Magnetic to Grid • LSRA (Left Subtract/Right Add)
