Chapter 2: Mapping Our World Latitude and Longitude Types of Maps Remote Sensing

Latitude and Longitude The science of mapmaking is called cartography Use an imaginary grid of parallel lines and vertical lines to locate points on Earth exactly The grid line halfway between the north and south poles is called the equator, which separates Earth into two equal halves called the Northern Hemisphere and the Southern Hemisphere

Latitude Lines of latitude run parallel to the equator Latitude – the distance in degrees north or south of the equator The equator = 0° North Pole = 90° N South Pole = 90° S

Longitude Longitude is the distance in degrees east or west of the prime meridian The prime meridian represents 0° longitude which goes through Greenwich, England Points are numbered 0°-180° West if west of the prime meridian and 0° - 180° East if east of the prime meridian Lines aren’t in parallel to measure longitude, they are in semicircles from pole to pole

Time Zones Earth is divided into 24 time zones Time is always changing because the Earth is ALWAYS spinning Each time zone is 15°, roughly corresponding to lines of longitude There are 6 different time zones in the United States Alaska Standard Time, Hawaii-Aleutian Standard Time, Pacific, Mountain, Central, Eastern

Calendar Dates Each time you travel through a time zone, you gain/lose time until, at some point, you gain/lose an entire day The 180° Prime Meridian is also called the International Date Line, which serves as the transition line for calendar days If you were going west across the line, you would add one day If you were going east across the line, you would lose a day

Types of Maps Mercator Projections Conic Projections Gnomonic Projections Topographic Maps

Mercator Projections A map that has parallel lines of latitude and longitude Landmasses at the poles are exaggerated Shapes of landmasses are correct, but their areas are distorted ex. Greenland and Australia Used for plane and ship navigation

Conic Projections Made by projecting points and lines from a globe onto a cone Used to make road maps and weather maps Highly accurate for small areas Distortion near the top and bottom

Gnomonic Projections Made by projecting points and lines from a globe onto a piece of paper that touches the globe at a single point These projections distort direction and distance between landmasses Used in plotting long-distance trips by air and by sea Great circles – parallels are shown as circles around the pole Only show one hemisphere at a time w/ distortion near the equator

Gnomonic Projections

Topographic Maps Topographic maps show changes in elevation of Earth’s surface Detailed maps showing the hills and valleys of an area, also show mountains, rivers, forests, bridges, etc. Use lines, symbols, colors to represent changes in elevation and features on Earth’s surface

Topographic Maps

Topographic Maps Contour Intervals – the space between side-by-side contour lines that shows difference in elevations Index Contours – Numbers that represent elevations on contour lines Depression Contour Lines – Represent features with lower elevations than their surroundings, like craters and mines Hachures – short lines at right angles to the contour line to indicate depressions (Figure 2-10 in your book) point toward lower elevations

Map Legends Map legends explain what the symbols on maps represent

Map Scale The ratio between distances on a map and actual distances on the surface of Earth Verbal scales – express distance as a statement Ex. “one centimeter is equal to one kilometer” Graphic scales – consists of a line that represents a certain distance Fractional scales – expresses distance as a ratio Ex. 1:63 500 - One centimeter on the map would be equivalent to 63 500 cm on Earth’s surface

Remote Sensing Remote sensing is the process of collecting data about Earth from far above Earth’s surface Satellites gather information about Earth’s surface

The Electromagnetic Spectrum The electromagnetic spectrum is the arrangement of electromagnetic radiation according to wavelengths Satellites detect different wavelengths of energy reflected from Earth’s surface All electromagnetic waves travel at the speed of light (300,000 km/s) Different waves can be described according to wavelength and/or frequency Frequency – the number of waves that pass a particular point each second

The Electromagnetic Spectrum

Landsat Satellites Receives reflected wavelengths of energy emitted by Earth’s surface Features on Earth’s surface radiate warmth at different frequencies, so they show up different in images from satellites Landsat satellites have a moving mirror with rows of detectors that measure energy when it scans the surface of the Earth Landsat data used to study movements of Earth’s plates, rivers, earthquakes, pollution

Topex/Poseidon Satellite Use radar to map features on the ocean floor by using high-frequency signals transmitted from the satellite to the ocean surface The returning echo is reflected off the water Used to study tidal changes and global ocean currents

Global Positioning System GPS is a radio-navigation system of many satellites that allow users to determine their exact position on Earth The satellites orbit Earth and transmit microwaves with info. about the satellites position Receivers calculate the users precise latitude and longitude by processing the signals emitted by the satellites

Sea Beam Used to map the ocean floor Located on a ship which uses sonar (sound waves) to detect and measure objects underwater Sound waves are sent from the ship to the ocean floor and an echo is returned after bouncing off the seafloor Computers calculate the distance to the bottom