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Chapter 2

Chapter Two.docx

7 Pages

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Geography 1400F/G
Godwin Arku

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Geography 1400g Chapter Two: Geographic Research and Maps January 16, 2012 A Research Question: What is the Influence of Place on Human Health?  Human health reflects complex interplay two general characteristics: individuals (age, structure, lifestyles) and circumstances in which they live both environmental and social  Considerable research on relationship of individual factors (smoking) as well as causal relationships between different environmental conditions and health Maps  H.J. de Blij, “if a picture is worth a thousand words, a map can be worth a million- but beware” because can distort reality, use generalization, symbolization to highlight critical info and suppress lower priority details  Map is two dimensional spatial representation of any part of our world Map Projections  A map projection is system for displaying curved surface of earth on flat sheet of paper  Cartographer tries to flatten earth, something always wrong, duty to select and preserve those relationships important for the purpose at hand, and to minimize those distortions that are inevitable but unimportant  Best way to model earth’s surface accurately would be show it on a globe, not as convenient as flat maps  Geographers make two different demands o Show at a glance generalized relationships and spatial content of entire world (have purpose) o Show detailed content of portions of earth’s surface-cities, regions, countries- without reference to areas outside zone of interest  To make world map, must decide how to peel map and flatten: either shows tears or stretching Projections: Geometrical and Mathematical  Task of geographers to construct on flat surface the network of parallels and meridians (the graticule)  A geometrical (perspective) projection (imagined light source inside), graticule is visually transferred from globe to geometrical figure, such as plane, cylinder, which can be cut, spread out flat o Surfaces of cylinders, cones, said to be developable surfaces (can be cut, laid flat without distortion) o Location of theoretical light source in relation to globe surface cause significant variation in projection of graticule on developable geometric surface  Orthographic projection results from placement of light source at infinity  Gnomonic projection is type of planer projection and is produced when light source is at centre of earth  When light is placed at antipode- point exactly opposite point of tangency (point of contact between globe and map) a stereographic projection is produced  Each projection scheme presents different arrangement of globe grid to minimize some distortions inherent Globe Properties and Map Distortions  All flat maps distort in different ways: area, shape, distance, and direction Area  Cartographers use equal-area or equivalent projections when important for map to show areas of regions in correct or constant proportion to earth reality  To compare amount of land in two different parts of world, would be misleading visually to use map that represented same amount of surface area at two different scales  To achieve equivalence, any scale change the projection portrays in one direction must be change in opposite  A map that shows correct relationships always distorts the shapes of regions Shape  No projection reproduce correct shapes for large areas, but some accurately portray shapes of small areas Geography 1400g Chapter Two: Geographic Research and Maps January 16, 2012  True-shape projections called conformal, and importance of conformality is that regions and features “look right” and have the correct directional relationships (achieved by ensuring latitude and longitude cross at right angles and scale is same in all directions at any given location  Except for very small area maps, a map cannot be both equivalent and conformal Distance  Distance relationships almost always distorted, some maintain true distances in one direction  True distance relationships mean length of straight line between two points on map correctly represent great circle distance between those points on the earth (an arc of great circle is shortest distance between two points on the earth’s curved surface; equator is great circle and all meridians of longitude are half)  Equidistant maps true distance in all directions is shown from one or two central points, all other locations are incorrect and greatly distorted Direction  On azimuthal projections true directions shown from one central point to all other points (azimuth is angle formed at beginning point of straight line, in relation to meridian)  Directions from points other than central point to other points are not accurate Which is best? - Mercator projection (wall maps) best used as a navigation aid because direction is maintained, amount of distortion increases as move away from equator (northern and southern masses appear larger) - Gall-Peters better represents area but distorts shape, scale, distance - Compromise is Robinson projection, neither equal area nor conformal, however it produces more appealing visualization (later switched to Winkel-Tripel) - Winkel-Tripel projection modification, minimizes distortion relative to shapes, distances, perspective Map Scale - Vital element of every map, generalizes data - Scale: relationship between size or length of feature on map and same item on earth’s surface, determines the amount of that generalization - Larger the fractional value, larger the scale The Globe Grid - Key reference points in grid system are North and South poles and equator and prime meridian - Latitude measures distance north and south of the equator and parallels run east-west - Longitude is angular distance of east and west of prime meridian and depicted by north-south lines Properties of globe grid that mapmakers retain are: 1. All meridians are of equal length; each is one-half the length of the equator 2. All meridians converge at the poles and are true north-south lines 3. All lines of latitude (parallels) are parallel to equator and to each other 4. Parallels decrease in length as one nears the poles 5. Meridians and parallels intersect at right angles 6. The scale on the surface of the globe is the same in every direction How maps show location - General-purpose, reference, or location maps make up one major class, purpose to show without analysis or interpretation a variety of natural or human-made features of an area or world as a whole (highway, street) - Since latitude and longitude are difficult to use, Military Grid, Civilian Grid System, and Universal Transverse Mercator (UTM) coordinate system have been developed Geography 1400g Chapter Two: Geographic Research and Maps January 16, 2012 - UTM often incorporated into GPS systems, based on grid pattern that divides earth into 60 zones, each with 60 degrees of longitude (starting at International Date Line (180 degrees) and proceeding east) - Canada spans zones 7 through 22 - Twenty UTM zones span 80 degrees south to 84 degrees north, each lettered C through X (without I or O), each band is 8 degrees wide - Location expressed as distance in metres to east of central meridian referred to as “easting” and distance in metres to north of equator referred to as “northing” - Northings measures positively from equator north - UTM integrated into Canada’s Nationals Topographic System How maps show other data- Thematic Maps th - Until 18 century, general-purpose map was dominant and primary function of mapmaker was to “fill in” world’s unknown areas with reliable locational information - Time passed, scholars wanted to accumulate locational info to display and study spatial patterns of social and physical data (climate, vegetation, soil, population), introduction of thematic map - Thematic map is general term applied to map of any scale that presents a specific spatial distribution or a single category of data (presents a graphic theme) - May be qualitative (show distribution of particular class of info) which show distribution of parks, pattern of agricultural specialization or quantitative (show spatial characteristic of numerical data) like population or average land value o Graduated Circle maps use circles of different size to show frequency of occurrence of topic in different places; larger the circle, more frequent the incidence o Dot maps have a single or specified number of occurrences of item studied recorded by single dot o Isometric maps feature lines connect points registering equal values of item mapped. Isopleth maps feature calculation referring to areal statistic and isoline connects average values o Choropleth maps present average value of data studied per pre-existing areal unit o Statistical maps record actual numbers of occurrences of mapped item per established unit area or location, a cartogram uses such statistical data to transform territorial space so that
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