Maps I: A Visualization Tool
Goals
Introduce longitude and latitude
Describe the components of a map
Show how spatial data are represented on contour maps
Introduce the contour profile
Explain the tier and range system
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Introduction
Maps are important to everyone. City maps help delivery companies get packages to us. We follow highway maps across the country. Aeronautical charts guide airline pilots around the world. Hikers, hunters, and foresters visualize the surface of the land using topographic maps. Although map making began centuries ago, maps are even more important in todayís technological society. Land ownership must be precisely recorded, flood-prone areas identified, productive agricultural land surveyed, and the spread of disease documented.

Because they represent the Earthís surface, maps cannot convey all the information about the surface. Some data must be omitted and other data generalized to keep the map from becoming too cluttered. A mapís purpose(s) determines what information is included. For example, water ownership maps would show streams and lakes but probably omit information about geology. Not including some details produces a clear map that highlights the information it was created to show.
A mapmaker also must decide how accurately to represent global surface features. A highway map of Maine may depict the seacoast with less detail than the highways, whereas a navigational chart will show the shoreline in great detail but might omit information about coastal roads.
Maps are used to accomplish three goals:
  1. Locate places
  2. Show distribution patterns
  3. Compare and contrast information
Some of the types of data portrayed on maps include
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  • Political: countries, states or provinces, or cities
  • Physical: mountains, rivers, continents, oceans, lakes, and streams
  • Road: roads, railroads, airports, and ports
  • Thematic: any information that varies spatially, such as soil types, Earth resources, and water sources
  • Weather: cold fronts, storm centers, and types and amounts of precipitation
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Various types of maps can be combined. For example, a political thematic map might show the distribution of population, land ownership, or†other man-made features. Although positional data should not change with time, other information portrayed on a map may have a limited period of use. Political maps may be accurate for decades or perhaps for only several years. Weather maps are useful for only a few hours. Geologic maps should remain useful for many years.
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