Maps: Geography s Basic Tools

Transcription

1 Maps: Geography s Basic Tools

2 What is a map? - A map is a representation of the earth s features drawn on a flat surface. - Maps use points, lines, colours, and symbols to represent the features of an area. - v=x4wgfshzxbg

3 Map Projections - Used to portray all or part of the round Earth on a flat surface - It cannot be done without some distortion. - Every projection has its own set of advantages and disadvantages. There is no best projection. - The mapmaker must select the one best suited to the needs, reducing distortion of the most important features. - Every flat map misrepresents the surface of the Earth in some way. No map can rival a globe; however, a map or parts of a map can show one or more - but never all- of the following: true directions, true distances, true areas, true shapes.

4 Distortions can include: - Direction Distance Area Shape Some maps need to sacrifice some accuracy to achieve its goal.

5 Cylindrical Projection - Projection in which meridians are mapped to equally spaced vertical lines and circles of latitude (parallels) are mapped to horizontal lines - Ex. Mercator Projection (1569) - significant distortion occurs at the higher latitudes, where the parallels become further apart, and the poles cannot be shown Mercator maps are used for naval navigation and calculating distances, but, unsuitable for general use as it makes some elements appear larger than they actually are.

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7 Conical Projection - We can visualize the Earth projected onto a cone, which is cut lengthwise and laid flat. - The parallels (lines of latitude), are represented by concentric circular arcs, and the meridians (lines of longitude), by straight, equally spaced, radiating lines. - Ex. Lambert Conformal Conic (for aeronautical directions) Conical Projections are also used as regional maps for mid-latitude nations/landforms. Most common map used at Statistics Canada to show their information

8 Lambert Conformal Conic

9 Planar and Azimuthal Projection (Part 1) - A portion of the Earth s surface is transformed from a perspective point to a flat surface. - In the polar case, the parallels are represented by a system of concentric circles sharing a common point of origin from which radiate the meridians, spaced at true angles. - This projection shows true direction only between the centre point and other locations on the map.

10 Planar and Azimuthal Projection (Part 2) - Any straight line drawn from the centre point on the map is on a great circle. The expression, great circle route, is the shortest path between two points the Earth. - This information is most useful in air navigation, because aircraft usually travel along great circle routes. - Example: Gnomonic (used for aeronautical navigation)

11 Planar or Azimuthal Projection(s) Examples:

12 Pseudo or Unique Projections - The many projections that cannot be easily related to the cylindrical, conical, or Planar surfaces are described as pseudo or unique. - They could be versions of a projection to which changes have been made to reduce or modify the pattern of distortion. - Example: Winkel Tripel Projection - (1921 by Oswald Winkel) - it does not eliminate area, direction, or distance distortions, rather, it tries to minimize the sum of all three; it provides the best balance between size, shape, distance, and direction; more realistic representation of the Earth; lines of latitude are slightly curved; replaced Robinson Projection (also pseudo) in 1998 by the National Geographic Society as the standard map representing the world.

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14 Maps: Geography s Basic Tool - Elements of a Map: 1. Title: identifies area shown and topic, purpose, or focus 2. Legend: explains meaning of symbols and colours 3. Scale: compares distance between points on the map with actual distance between those on the Earth s surface. Allows the reader to measure distance and to calculate area.

15 Elements of a map (cont d) - Elements of a Map: 4. Date of Publication: indicates if information is recent 5. Borders: set the map apart from other information 6. Directions - Compass: Represented in various ways: a. By direction arrow or symbol b. By the use of latitude and longitude

16 Types of Maps 1. General-Purpose Maps: provide many types of information on one map. Examples include Atlas maps, Wall Maps and Road maps. a. Things found on a general-purpose map include: bodies of water, roads, railway lines, parks, elevation, towns, and cities.

17 Types of Maps 2. Thematic Maps: provide very specific information about a place. They are designed to provide information on one particular topic.

18 Types of Maps 3. Topographic Maps: use symbols to show a variety of different features. They are very useful to examine the characteristics of a small area. Example: This map of an area around Banff, Alberta depicts relief (contour lines show elevation), rivers, railroads (natural and manmade features) in detail. It could be used for planning a hiking trip.