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  1. EARTH AND SPACE SCIENCE Chapter 3 Models of the Earth 3.2 Mapping Earth’s Surface

  2. 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.

  3. Introduction • A globe can accurately represent locations, relative areas, and relative shapes of Earth’s surface features since the globe is spherical – like the Earth! • The finer details of Earth’s surface cannot be accessed using a globe.

  4. How Scientists Make Maps • Cartography is the science of making maps. • Cartographers are scientists who make maps. • Cartographers use data from a variety of sources in order to make maps. • Field Survey – cartographer walks or drives through an area and takes measurements to be plotted on a map • Remote Sensing – images of the Earth taken from a plane or satellite are used to make maps • Combination of field surveys and remote sensing are often used to map an area

  5. Map Projections • A map is a flat representation of Earth’s curved surface. • Distortion in size, shape, distance, or direction may occur when transferring a curved surface area to a two dimensional map. • The larger the area represented on the map, the greater the distortion tends to be.

  6. Map Projections • A map projection is a flat map that represents the three-dimensional curved surface of Earth. • Though no projection is entirely accurate, some types of projection maps are more useful to us than others.

  7. Map Projections • Cylindrical (Mercator) projections are constructed with straight meridians and appear as if someone put a lighted globe in the middle of a paper cylinder with the paper only touching at the equator. • This map is accurate at the equator, but distorts size and distances near the poles. • Locating positions is easier on this type of map because of the grid created by making the meridians parallel. • The mapping of small areas is done this way because distortion of those areas is minimal.

  8. Map Projections • Azimuthal (Gnomonic) projections are made by putting a sheet of paper against a transparent lighted globe such that the paper touches the globe at only one point. • Very little distortion occurs at the point of contact on this type of map, yet the distortion increases as you move away from the point of contact. • Azimuthal projections show unequal spacing between parallels which results in distortion of distances and directions. • Azimuthal projections are useful for navigators to plot routes for air travel because drawing a straight line on an azimuthal projection is the shortest distance between two points on a globe.

  9. Map Projections • A conic projection is made by placing a paper cone over a lighted globe so that the axis of the cone aligns with the axis of the globe. • The cone touches the globe at one parallel of latitude. • Distortion is minimal at the point where the cone touches the latitude of the globe. • Polyconic projections, a series of conic projections used to make a map, are used to minimize distortion.

  10. Reading a Map • In order to read a map, one must be able to understand symbols and figure direction and distance. • Most maps are made so that north is at the top, east to the right, west to the left, and south to the bottom. • Lines of longitude are often parallel as well as lines of latitude being parallel. • A compass rose often is used to determine direction on the map.

  11. Reading a Map • Maps with multiple symbols will often have a legend – an explanation for what the symbols mean. • The scale of a map shows the relationship between the distance on the map and the actual distance. • Graphical scale – marked line similar to a ruler that will be of a specified distance • Fractional (ratio) scale – mathematic representation of the relationship, often a ratio of map distance to actual distance • Verbal scale – verbal expression of the distance relationship between the map and actual area

  12. References • Globe - • Topographic Map - • Cylindrical Projection Map - • Cylindrical Projection -

  13. References • Azimuthal Projection - • Azimuthal Projection Polar Map - • Polyconic Projections - • Conic Projection -

  14. References • Compass Rose - • Map Scale - • Map Legend -