Chapter 2: Maps as Models of the Earth How to Read a Map Chapter 2: Maps as Models of the Earth

How Can We “See” the Whole Earth? Satellites are the best way for us to see the Earth as a whole. Satellites orbiting the Earth are constantly taking pictures of everything! Remote sensing helps us to see things we can’t readily see, like the ocean floor. Maps help us to see smaller areas of the Earth, and come in a variety of types such as road, weather, and topographic.

So, Where are We Going? When you are giving someone directions to your house, you need to be specific so they don’t get lost! Usually, we use the north and south poles as reference points. Along with east and west, these are called cardinal directions. A compass will help you find these cardinal directions. It will actually point you in the direction of the magnetic north pole or magnetic south pole. Our magnetic axis is tilted 23.5o from geographic north, or true north. The angle of correction between these is called magnetic declination.

Using Latitude and Longitude Lines of latitude are the horizontal lines on a map. They are measured north and south of the equator (0o). 90o N is the north pole and 90o S is the south pole. Lines of longitude are the vertical lines on a map and are measured east and west of the prime meridian (0o). There are 180o in each hemisphere. Where the east and west hemispheres meet is the International Date Line.

The International Date Line & Time Zones The International Date Line sits on the 180º line of longitude in the middle of the Pacific Ocean, which separates two consecutive calendar days. Immediately to the left of the International Date Line is always one day ahead of the date (or day) immediately to the right of the International Date Line. Earth's surface is divided into 24 time zones. The standard time of each zone is the mean astronomical time of one of 24 meridians, 15 degrees apart, beginning at the Greenwich, England, meridian and extending east and west around the globe to the International Date Line.

Breaking Degrees Down Cartographers (map-makers) further break down the degrees latitude and longitude into minutes, and break the minutes down into seconds. 1 degree = 60 minutes & 1 minute = 60 seconds Why do this? To be more accurate in finding locations on a map. What does this look like on a map? If we said our latitude was 45 degrees, 32 minutes, and 14 seconds, it would look like this: 45o 32’ 14”.

Map Projections Mercator: has accurate sizes of continents near the equator, but more distorted at the poles. Latitude and longitude lines are parallel but are spaced farther apart the closer you get to the poles. Conic: transferring a globe onto a cone and then flattening it out. Does not distort the continents. Robinson: parallel latitude lines, curved longitude lines causing the distortion of continents near the poles.