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Chapter 2: Mapping Our World

Ch. 2.1 Latitude and Longitude

Lines of latitude and longitude are used to locate places on Earth

Latitude

Maps are flat models of three-dimensional objects.  Cartography- the science of map making. Use a imaginary grid of parallel lines to locate exact points on Earth.

Equator- horizontally circles Earth halfway between north and south poles. It separates Earth into equal halves: Northern and Southern hemispheres.

Latitude- lines running parallel to the equator, the distance north or south of equator in degrees. Equator is 0º, poles are 90º.

Degrees of Latitude

Each degree of latitude is equal to about 111km. Cartographers divide 360º by 40,000 (Earth circumference) to determine. Degrees of latitude broken down to minutes ( ' ). Each latitude is 1.85km 111km divided by 60. Minutes can be divided to seconds ( " ).

Longitude

Lines of longitude used to locate positions East and west, also called meridians. Longitude- the distance in degrees east or west of the prime meridian.

Prime Meridian- 0º longitude, goes through Greenwich, England

Semicircles

Lines of longitude are not parallel, run from pole to pole. Opposite the prime meridian is the International Date Line at 180º.

Degrees of longitude

Lines converge at poles, distance varies from 0km to 111km

Using Coordinates

Both latitude and longitude are needed to locate position on Earth precisely.

Time Zones

Earth divided into 24 time zones, one for each hour of day. Earth spins about 15º per hour so each time zone is about 15º, similar to lines of longitude. Time zone boundaries are adjusted around cities. Six time zones in U.S.

International Date Line

180º meridian, the transition line for calendar days. Runs through Pacific Ocean; traveling west across adds a day, east would lose a day.

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Ch. 2.2 Types of Maps

Cartographers use different maps for different purposes.

Projections

Difficult to represent Earth's spherical shape on a flat surface. All flat maps distort area or shapes of landmasses. A map projection is made by transferring points and lines on a globe's surface onto a sheet of paper.

Mercator projection- a map that has parallel lines of latitude and longitude. When lines of longitude are projected as being parallel on a map, landmasses near the poles are exaggerated. Shapes of landmasses are correct but area is distorted.

Most commonly used for the navigation of ships since land shapes are correct.

Conic projection- is made by projecting points and lines from a globe onto a paper cone. The cone touches a particular line of latitude. Distortion at the top and bottom of cone. Used for road maps and weather maps because it is accurate in small areas.

Gnomonic projections- made by projecting points and lines from a globe onto a piece of paper that touches the globe at a single point. No distortion at that point, outside that point is great amounts of distortion in direction and landmasses. Useful for navigation; the straightest route from one point to another.

Play Video of Projections

Topographic Maps

Maps showing hills and valleys of an area. Topographic maps- show changes in elevation of Earth's surface. Use lines, symbols, and colors to represent changes in elevation & features.

Contour Lines

Elevation is represented by a contour line. Elevation refers to the distance above or below sea level. Contour line- connects point of equal elevation; they never cross.

Contour Intervals- the difference in elevation between two side-by-side contour lines. Contour interval is dependent on the terrain.

Index Contours Some contour lines are marked by numbers representing their elevations.

Depression Contour Lines Used to represent elevations that are lower than that of the surrounding landscape. Contour lines with short lines at right angles to the contour line (hachures). Hachures point towards the depression.

*When going uphill; the first depression contour line is that same elevation as the contour line before it.

Geologic Maps

Geologic maps- used to show distribution, arrangement, and type of rocks below the soil. May also show features: fault lines, bedrock, and geologic formations.

Often superimposed over topographic maps and color coded by the type of rock formation. Each color represents a type of rock; symbols present to show mineral deposits and structural features.

Three-dimensional maps

Topographic and geologic maps are two-dimensional, computers can be used to digitize features such as rivers, mountains, valleys, and hills.

Map Legends

Human made and natural features are represented by symbols, such as black dotted lines for trails, solid red lines for highways, and small black squares and rectangles for buildings.

Map legend- explains what the symbols represent

Map Scales

Measuring distance is important when using a map. Map scale- the ratio between distances on a map and actual distances on the surface of Earth. Usually in SI, but sometimes they are measured in different units such as miles and inches. Three types of map scales: verbal scales, graphic scales, and fractional scales.

Verbal Scale: expresses distance as a statement. "one centimeter is equal to one kilometer"

Graphic scales: consist of a line that represents a certain distance, such as 5km or 5 miles. Graphic scales are the most common type of map scale.

Fractional scales: express distance as a ratio such as 1:63,500 which means one unit of distance on the map is equal to 63,500 units of distance on Earth's surface. Large ratio indicates a large area, small ratio is small area.

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Ch. 2.3 Remote Sensing

New technologies have changed the appearances and uses of maps.

Landsat Satellite

Remote sensing- process of gathering data about Earth using instruments mounted on satellites, airplanes, or ships.

Landsat Satellite- record reflected wavelengths of energy from Earth's surface. Features on Earth radiate warmth at slightly different frequencies; including visible light and infrared radiation. Computers then convert the information into digital images of great detail. Often used for natural disasters.

OSTM/Jason Satellites

Uses radar to map sea surface height. OSTM- Ocean Surface Topography Mission. Uses high frequency signals reflected off the ocean surface. Uses known speed of light to and time for signal to be reflected to calculate variations in sea level.

Accurate to within millimeters. Bulges in sea level indicate ridges and depressions indicate valleys. Also used for forecasting El Nino or warm currents.

SeaBeam

Similar to OSTM but on a ship and maps ocean floor instead of surface. Uses sonar; sound waves to detect and measure objects. Uses the known speed of sound in water and the time it takes for the sound to be received.

The Global Positioning System

Global positioning system (gps)- a satellite navigation system used to locate approximate position on Earth. Need a gps receiver which calculates approximate latitude and longitude. 24 orbiting satellites for use. Three satellites can give location, four can give location with elevation.

Uses for GPS technology

Navigation by airplanes and ships, automobiles, hiking, etc.

The Geographic Information System

Geographic information system (GIS)- combines many types and styles of mapping to create layers, or "themes" of information to create a comprehensive map. Might contain many layers of information compiled from several different types of maps.

GIS maps can be updated as new information is loaded in database. Linked layers then also change for up-to-date map.

 

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