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

Uses:

  • 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.

Uses:

  • 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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