Monday, April 26, 2010

Introduction to reference: Geographic sources

Geographic sources
  • help to locate places
  • usually deal with a time period, either current or historical
  • some deal with thematic or subject info
Categories of locational questions
  • current events
  • recreation
  • business
Historical geography
  • genealogy
  • military history
  • place name changes
Map: a drawing of all or part of the earth or universe, usually produced on a flat surface and almost always at a greatly reduced scale. • Physical maps: trace various features of the land, e.g. lakes, rivers, mountains. • Route maps: show features such as roads, railroads, bridges, hiking trails. • Political maps: show various political boundaries eg. towns, cities, counties, countries Some maps include all three types of info. Large flat maps provide the most detailed geographic info. Uses:
  • finding details of a local area such as streets, public buildings, churches, schools
  • look at growth or decline of an area
  • look at topography, drainage systems, woodland cover, and other physical and cultural features
Atlas: a planned or systematic collection of geographical maps bound in book form or kept loose in a binder or slipcase. Can provide whole world in one volume at nominal cost.
  • Geographical: show important geographical or political features of the world.
  • Historical: show boundary changes, military campaigns, or early exploration.
  • Thematic: emphasize a specific subject or region, include national, population and geographical atlases
  • locate places, countries
  • understand historical development of a country or region
  • look at a specific subject or theme in more detail e.g. world population
Gazetteer: geographical dictionary, usually of place names or physical features. Compliment and supplement atlases. Can be part of an atlas like an index or be separate publications.
  • Locational: provide info for precise location of feature either by atlas page and grid index or by latitude and longitude
  • Descriptive: locational info plus description e.g. brief history, population, altitude, commodities, etc.
  • Find where a specific city, mountain, river, or other physical feature is located
  • Find additional info such as population or perhaps leading economic characteristics of an area.
Cartography: the art and science of map making. Cartographer: a map maker. Travel guides: provide info about a place or country written to meet the needs of a particular group e.g. students, or level, e.g. inexperienced, traveler. May be written to meet the needs of the armchair traveler. Uses:
  • inform travelers about what to see, where to stay, where to eat and how to get there
  • provides a lot of detail about specific places e.g. museums, restaurants, art galleries, historic attractions, churches, etc.
The only relatively accurate graphical representation of the earth is a globe but the need for a globe in a reference situation is probably questionable. Evaluation criteria Maps and atlases have unique evaluation criteria Scale and projection
  • Scale: ratio of distance on map to actual distance in real world
  • Projection: method used to transfer a curved section of the earth to a flat, two dimensional surface.
Scale: most important element of a map as it defines the amount of info that can be shown, as well as the size of the geographical area.
  • The smaller the right hand number, the larger the scale of the map 1:75,000 is a larger scale map than 1:600,000 which is a small scale map.
  • The larger the scale, the smaller the area the map can cover, but the greater amount of detail that it can include about that area.
  • Scales given in numbers called representative fractions (RF):
    1:100,000 means one unit of distance on the map equals 100,000 of the same unit on the surface being portrayed, e.g. the earth
  • Small-scale maps are used for maps of wide areas where not much detail is required. For example, a small-scale map of Europe (e.g. 1:12,000,000) would fit on a single page (typically 8 inches by 11 inches).
  • A medium-scale map of San Francisco (e.g. 1:300,000) would fit on a single page.
  • Large-scale means a more detailed map. They are used in large applications where detailed local maps are required. A large-scale map of a small town (e.g. 1:24,000) would fit on a single page.
Projection All maps are imprecise because projection of the earth’s curved surface onto a flat surface results in some distortion. To minimize or control distortion cartographers have developed numerous scientific map projections each of which has its own special uses, e.g. on world maps:
  • Mercator projection shows correct shape of land masses but distorts their size.
  • Google’s Interrupted Homolosine projection allows fairly faithful representation of both the shape and size of large land masses but distorts and interrupts the ocean area.
Mercator projection Goode's interrupted Homolosine Colour and symbols Colour used for: political boundaries, contour lines, water, roads, railways, buildings, highways, vegetation, etc. Symbols: amount and type controlled by scale of map Map should be legible and easy to interpret. It should not be too cluttered. Publisher/Authority
  • national mapping authority
  • Rand McNally, C.S. Hammond, National Geographic Society, John Bartholomew, Oxford University Press, Michelin
Indexing/Place-names As a rule, atlases lacking a general index, or at least separate map indexes should be avoided.
  • Does index include all places and features shown on maps?
  • Approx. how many entries are included?
  • Single alphabet at back or separate indexes for each map or series of maps?
  • Does index effectively refer you to right map and right point on map?
  • How are variant place-names treated, and is there adequate cross-referencing?
  • Does index offer any info beyond place-names and map references e.g. pronunciations, population stats?
Currency Copyright date and date when maps prepared can vary widely. May represent a new printing with only minor corrections vs. a new edition with major revisions.

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