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Section 3.2 Mapping Earth’s Surface Objectives Explain two ways that scientists get data to make maps. Describe the characteristics and uses of three types of map projections. Summarize how to use keys, legends, and scales to read maps. Map of Babylon About 600 B.C.

Scale is Everything Globes are good for showing large scale features, but bad for small. How big would a globe have to be if I only wanted to look at the Snoqualmie Valley?

Extremely Difficult How do you put what is on the surface of a sphere onto a flat piece of paper?

How Scientists Make Maps The science of map making is called cartography. It is a subfield of earth science and geography. Scientists who make maps are called cartographers. They use a variety of sources to make maps.

Field Surveys They walk or drive through an area and make measurements that are plotted on a map. Not all points can be measured, so estimation between surveyed points are common.

Remote Sensing Gathering and analyzing information without being in physical contact with the object. Examples: Using satellites and airplanes. Radar Map of Our Area

Often Used In Combination Using information from both field surveys and remote sensing.

Map Projections A map (flat representation) that represent the three dimensional curved surface of a globe. Made by imagining the earth as being transparent with a light inside. Hold a piece of paper against the globe, and the shadows can be marked on the paper.

Distortion Caused by transferring the curved surface of the earth to the flat surface of a map. Map projections are 100% accurate where the paper touches the globe. The further away the map is from where the paper touches, the more distorted the map is.

Many Different Types We will examine only 3: Cylindrical Azimuthal Conic Each have advantages and disadvantages.

Cylindrical Projection A cylinder of paper is wrapped around the globe. It is accurate at the equator, but distorted at the poles.

Advantages Meridians appear as straight, parallel lines; this forms a grid which makes locating positions easier. Shapes of small areas are well preserved. In mapping small areas, distortion is minimal.

Disadvantages Accurate near the equator, but distorts distances and sizes near the poles.

AZIMUTHAL PROJECTIONS A sheet of paper touches a lighted globe at only one point.

Disadvantages Distortion in both direction and distance is greatest at the edges of the map.

Advantages Mapping the polar regions and for air navigation. Great circle routes are straight lines.

CONIC PROJECTIONS A cone is placed over a lighted globe so that the axis of the cone aligns with the axis of the globe. The globe touches the paper along one line of latitude.

Advantages No distortion along the line of latitude used.

Polyconic Projections Using a series of conic projections to map neighboring areas and then fitting the adjoining areas together.

Advantages The relative size and shape of small areas are nearly the same as those on a globe.

Reading A Map You must be able to understand the symbols used, be able to find directions, and calculate distances.

Direction on a Map Usually, for a cylindrical projection, a compass rose is used to show the 4 cardinal directions (sometimes a single arrow is used to point to geographic north). Usually parallels run east-west and meridians north-south (but not always). Compass Rose

For Azimuthal and Conic Projections Direction should always be determined in relation to the parallels and meridians.

Symbols Explained in the map legend (or key), a list of the symbols and their meaning. Some are abstract and some may resemble the features they represent.

Map Scales This indicates the relationship between distance shown on the map and actual distance. Can be shown three ways:

A Graphic Scale A printed line divided into equal parts and labeled with the units of measurement. You measure a distance on the map and compare it to the scale.

Fractional Scale Usually given as a ratio. An example would be 1: Thus one cm on the map equals cm (0.24 km) in the real world.

Verbal Scale A written statement on the map stating the scale. Example: “One centimeter equals one kilometer”

Isograms Greek: iso = “equal” gram = “drawing” A line on a map representing a constant or equal value of a given quantity. The gram part of the word may be changed to show what is being measured

Examples Isothermic map: lines connecting points of equal temperature. Isobaric map: lines showing the same air pressure

ASSIGNMENT Directed Reading 3.2 Key Terms Yee-hah!!!