Map Reading Basic

Map Basics Definition: A map is a mathematically determined representation of the Earth’s surface systematically plotted to scale upon a plane surface. 2/27/2019 NROTC Unit, UC Berkeley

Map Basics: Marginal Information (cont.) PRIMARY SCALE 1000 2000 3000 4000 5000 500 METERS EXTENSION SCALE 2/27/2019 NROTC Unit, UC Berkeley

Marginal Information (cont.) Map Basics: Marginal Information (cont.) Declination Diagram True North Grid North Magnetic North 2/27/2019 NROTC Unit, UC Berkeley

Map Basics: Declination Diagram GRID NORTH TRUE NORTH Note: See Declination Diagram on Handout Map MAGNETIC NORTH 2/27/2019 NROTC Unit, UC Berkeley

Map Basics: 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 2/27/2019 NROTC Unit, UC Berkeley

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 2/27/2019 NROTC Unit, UC Berkeley

Map Basics: Colors Black: Man-made objects Red: Main roads 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. 2/27/2019 NROTC Unit, UC Berkeley

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 2/27/2019 NROTC Unit, UC Berkeley

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 2/27/2019 NROTC Unit, UC Berkeley

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 2/27/2019 NROTC Unit, UC Berkeley

Contour Lines: Basics 10 2 1 x358 3 4 5 350 6 9 300 8 7 Supplementary Contour Line Intermediate Contour Line Index Contour Line 2/27/2019 NROTC Unit, UC Berkeley

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 2/27/2019 NROTC Unit, UC Berkeley

Contour Lines: Elevation 350 300 1 2 3 4 5 6 7 8 x358 9 10 Elevation of Point: 7 = ? 3 = ? 9 = ? 1 = ? 4 = ? 8 = ? 10 = ? 2/27/2019 NROTC Unit, UC Berkeley

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 2/27/2019 NROTC Unit, UC Berkeley

Relief & Terrain Features: Slopes Uniform Gentle Slope Uniform Steep Slope Convex Slope Concave Slope 2/27/2019 NROTC Unit, UC Berkeley

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 2/27/2019 NROTC Unit, UC Berkeley

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 2/27/2019 NROTC Unit, UC Berkeley

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 2/27/2019 NROTC Unit, UC Berkeley

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 2/27/2019 NROTC Unit, UC Berkeley

Relief & Terrain Features: Terrain Features Cuts: places where high ground leveled off Fills: areas where low areas are filled in 2/27/2019 NROTC Unit, UC Berkeley