LAND NAVIGATION: The Topographic Map

Hill

-Area of high ground -contour lines will be concentric circles with the inside of smallest circle being the hilltop

Contour Lines

-Method used to depict the relief of a terrain -The continuous brown lines found on maps that give information about elevation -Each line represents a specific elevation, and all locations along that line have the same elevation

Supplementary Contour Lines

-Resembles dashes -show sudden changes in elevation of at least 1/2 the contour interval -normally found where there is little change in elevation

Index Contour Lines

-Starting at zero elevation, every 5th contour line is a heavier line which are known as index contour lines -Each index contour line is numbered at some point. This number is the elevation of that line.

What is the Marginal Information? -Why important to read this every time a different map is used?

-The instructions that are placed around the outer edges of a map -Provides the useful instructions necessary to read the map -Since all maps aren't the same, it's necessary to read them every time a different map is used.

What is the purpose of a Topographic map?

-To provide information on the existence, the location of, and distance between ground features -to indicate variations in terrain, heights of natural features, and vegetation cover -To permit the user to visualize an area of earth's surface with pertinent features properly positioned

Black

-roads & buildings (man-made) (buildings, houses, smaller roads, trails, political boundaries)

What are the 3 different types of Contour Lines?

1-Index 2-Intermediate 3-Supplementary

Saddle

A dip or low point between 2 areas of higher ground -has high ground in 2 opposite directions and low ground in the other 2 opposite directions -Contour lines will form either an hourglass or figure-eight shape

Draw

A less developed stream course than a valley -will slope up in 3 directions and down in other direction -Contour Lines will form either a U or V shape pointing toward the high ground

Define Ridgeline

A line of high ground, usually with changes in elevation along its top, and low ground on all sides

Legend

A list that identifies patterns, symbols, or colors used in a chart

Depression

A low point in the ground or a sinkhole -Contour Lines will be closed with tick marks that point toward the low ground

Cut

A man-made feature resulting from cutting through high ground, usually to form a level bed for a road or railroad track -Contour lines will extend length of the cut and has tick marks that extend from the cut line to railroad tracks

Fill

A man-made feature resulting from filling a low area, usually to form a level be for a road or railroad track -Contour lines will extend length of the filled area and has tick marks that point toward low ground

Finger

A short continuous sloping line of higher ground, normally jutting out from the side of a ridge -Contour lines will form a U or V pointing away from the higher ground

Ridge

A sloping line of high ground -normally has low ground in 3 directions and high ground in other direction, with varying degrees of slopes -Contour Lines will form either a U or V shape, with the closed end of the contour line pointing away from high ground

Valley contour lines

A stretched-out groove in the land, usually formed by streams or rivers -has high ground in 2 opposite directions and a gradual inclination in the other 2 directions -Contour lines will form either a U-shape or V shape

Cliff

A vertical, or near vertical feature; it is an abrupt change of the land -When a slope is very steep, contour lines will converge into one "carrying" contour line, with the last line having ticks that point toward low ground

Steep Slope

Contour lines are close together -Contour lines will be uniform in shape and evenly paced, but closer together

Concave Slope

Contour lines will be closely spaced at the top and widely spaced at the bottom

Convex Slope

Contour lines will be widely spaced at the top and closely spaced at the bottom

Red

Cultural Features (populated areas, larger man-made features, major highways and roads)

Intermediate Contour Line

Falls between the index contour lines -are finer and don't have their elevations identified -normally there are 4 intermediate contour lines between index contour lines

Declination Diagram

Indicates the angular relationships of true north, grid north, and magnetic north. How to do it: 1-Make sure to first orient the map using your compass to true north 2-The convert from grid north (map) to magnetic north (compass)

What is a Topographic Map?

It is a graphic representation of a portion of the earth's surface drawn to scale, as seen from above -uses colors, symbols, and labels to represent features found on the ground -portrays terrain features in a measurable way, as well as the horizontal positions of the features represented

Terrain Features are classified as either:

Major, Minor, or Supplementary

Reddish Brown/ Brown

Relief & Elevation (used in the form of contour lines)

Spot Elevations

Specifically labeled elevations on a topographic map -The heights between contour lines, and are shown on the map as dots with a value beside them

Define Slope

The ratio of rise or fall of a terrain feature -Can be determined by studying the contour lines on a map: ^ The closer the contour lines, the steeper the slope ^The farther apart the contour lines, the gentler the slope

Map Scale

The relationship between the size of an object on a map and the size of the actual feature on Earth's surface. -The smaller the scale ratio (ex. 1:10,000), the greater the map detail -The larger the scale ratio (ex. 1: 50,000), the less detail the map will have since cramming more information

Definition of Relief

The representation of the shapes of hills, valleys, streams, and terrain features on the earth's surface

Definition of Elevation

The vertical distance of an earth's surface above or below mean sea level

Adjoining Sheets

Usually 9 squares with the current map sheet being the center square -the 8 surrounding squares tell you what the next map over would be -helps you know what other map you may need to cover your operation if it bleeds over

Green

Vegetation

Blue

Water (lakes, rivers, streams, swamps)

Terrain features are derived from...

a complex land mass known as a ridgeline

Bar Scale

a graphic that compares the distance on a map to the actual distance it represents

Bench Mark (BM)

a location where an exact elevation is known -a marker that was placed in the ground when the surveyors were out making the map

Gentle Slope

shown by widely spaced contour lines -Contour lines will be uniform in shape and evenly spaced, but far apart from each other

Contour Interval

the difference in elevation between one contour line and the next (vertical distance between contour lines)