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Data Classroom



Maps: What Are They? Maps depict, most commonly on a flat surface, the spatial organization of any part of the physical universe at any scale, and at the same time symbolize a wide variety of information, both static and dynamic. Whether it be a chart of outer space or a plan of a university campus, maps play an essential role in our everyday lives. Cartography is the art and science of map production. It applies the fundamental scientific procedures of accurate measurement, classification, and the identification of relationships, to create visual models of our complex world. Globes and Maps A globe is a true representation or model of the Earth's surface, but, its use has limitations. You can view only one side of the Earth at a time. Usually the size or scale is too small to be useful and large globes are difficult to handle. Maps, however, are much more versatile. Flat maps can be rolled or folded and are, therefore, portable. Maps are reproducable in large quantities. When in digital form, they can be displayed on a computer. The Classification of Maps There are many ways to classify maps, based on different criteria, such as scale, projection, or content. However, in the field of cartographic production, maps usually fall into two categories: base maps and thematic maps. Base Maps depict fundamental information about the Earth's surface such as landforms and drainage. They also symbolize landmark features like roads, railways, populated places and buildings. Many features are also identified by geographical names and labels. Maps that provide only 2-dimensional information are called planimetric, whereas those that also depict elevation are called topographic. Cadastral Topographic Elevation on topographic maps can be indicated in various ways. The most commonly used method is to plot contour lines joining points of equal height or depth. The difference in elevation between contour lines is known as the contour interval. Specific points of known elevation, called spot heights, are often included to provide more accurate information. Another method of showing topography is relief shading, an artistic impression of elevation, which creates a 3-dimensional view. The addition of colour between selected contour intervals also serves to highlight elevation or depth. These colours are called hypsometric tints. Relief Shading Hypsometric Tints Base maps are produced at various scales, covering a wide range of areas, such as provinces, countries, continents or the entire world. Often, maps are available as a series, such as the 1:50 000 and 1:250 000 scale National Topographic System (NTS), produced by Centre for Topographic Information. Thematic Maps show the spatial distribution of a wide variety of qualitative and quantitative information. In fact, almost any subject that can be expressed as a geographical distribution can be mapped. Qualitative thematic maps depict the distribution of nominal data (data which is classified without hierarchy). Examples of this type of map would show the location of different types of precipitation (e.g., rain, snow, hail, etc.), vegetation or employment. Qualitative Map Quantitative thematic maps are more complex, and involve the location of ordinal, interval, and ratio data. Ordinal data provides the map user with information about rank or hierarchy, for example, a map showing populated places classified as either city, town or village. Maps symbolizing interval or ratio data provide more precise information. They employ a scale of measurement, usually described in the map legend. For example, a rainfall map indicating the number of millimetres per year in different locations, would illustrate interval data. Quantitative Map How Maps are Used There are common patterns to the way humans perceive and organize their environment. In the process of responding to the demands of society, over the centuries people have unknowingly created spatial structures, which in turn have modified the environment. (Unplanned transportation networks are one example of such structures.) Cartography helps us to describe systematically, human activity in terrestrial space. This is even more feasible with digital cartography. By mapping thematic information and overlaying these layers of data in a GIS (Geographical Information System), we are able to analyze human spatial activity. Knowledge gained from this technology allows us to detect problems and plan strategies to manage our environment more successfully. Some maps are produced for specialized purposes. They usually occur in a series, often with a common scale. Examples are: Hydrographic charts -- essential for the safe navigation of water transportation routes. Aeronautical charts -- pilots rely on them for accurate information on flight paths and approaches to airports. Electoral maps show the boundaries and names of districts or ridings, which are determined by census data. The results of an election can be mapped at a national scale, by indicating with different area colours, the political party that won each district. Hydrographic Aeronautical Electoral Atlases An atlas is a collection of maps, usually published in book form, or, in the case of The National Atlas of Canada, 5th Edition, as a loose-leaf, boxed set. What often characterizes atlas maps is a standard design, organized around a coherent theme. Atlases are produced on a wide range of subjects. A national atlas provides base and thematic information about a particular country. The fundamental characteristics of the maps, as well as their scales are usually the same, thereby facilitating the comparison of different types of data. A world atlas of political maps will include various scales, depending on the amount of detail required to depict each region adequately. Finally, a gazetteer atlas shows detailed information about populated places and geographical features, with names and locations. The National Atlas of Canada, 5th Ed. National Atlas Map, 5th Ed. References: Abler, Ronald, Adams, John S., and Gould, Peter. 1971. Spatial Organization. Englewood Cliffs, N. J.: Prentice-Hall. Canada. Natural Resources Canada. Geomatics Canada, The National Atlas of Canada - 5th Edition. Ottawa. Raisz, Erwin. 1962. Principles of Cartography. New York: McGraw-Hill Book Company. Robinson, Arthur H., and Sale, Randall D. 1969. Elements of Cartography. Third edition. New York: John Wiley & Sons. For more examples of maps in general and for associated geographical information, see The Atlas of Canada home page. For a comprehensive bibliography of Canadian atlases, grouped by subject, see Canadian Atlases since 1945. SAMPLE TEST QUESTIONS ON THIS UNIT: 1. Give a brief explanation (not more than 30 words), for each of the following terms: a map, a globe and cartography. 2. For cartographic production, in what two categories do most maps fall? Give examples of each. 3. Briefly describe two methods used to depict elevation on maps. 4. Provide examples of the two general types of information portrayed on thematic maps? 5. Explain and give examples of nominal, ordinal and interval data. 6. Briefly explain how a GIS is related to mapping thematic data. 7. Give two examples of special purpose maps, and describe their importance. 8. What is an atlas? Provide examples of topics they cover. 9. Visit your library. Examine an atlas and describe three thematic maps that it contains. Provide a reference for the atlas (see examples above).

GIS Map 1
Description of the Map

GIS Map 2
Description of the Map

GIS Map 3
Description of the Map
www.rain.org/gis