1300 Chapter 2 - Maps

Cartography

• The science and art of making maps
• Maps are the primary tools of spatial analysis

Locating Points on a sphere: 360°

Latitude

• Degrees north or south of the equator
• Equator = 0°
• Poles = 90° North or South
• Each degree of Latitude = approximately 111km (69miles)
• degrees of latitude are slightly longer near the poles.
• Degrees of Latitude are then divided into 60 minutes (‘) and 60 seconds (“)
• One Minute of Latitude = approximately 1.85km (1.15 miles)
• One Second of Latitude = approximately 31 meters (101 feet)
• So when writing Latitude of Houston: 29° 58’ N

Longitude

• Degrees east or west of the Prime Meridian (180° each way)

• Prime Meridian
• Imaginary line passing through the Royal Observatory at Greenwich, England. (Selected by an international conference in 1884)
• Longitude is also divided into degrees, minutes, and seconds.
• Houston is at 95° 21' W
• Time zones are based on Longitude with each time-zone being approximately 15° wide.
• Time-zones and the International Date Line are modified for political considerations.
• Meridians are farthest apart at the equator and closest together at the poles.

True North and South are different from Magnetic North and South as the Magnetic North Pole tends to wander.

Map Projections

• Only a globe can accurately represent the Earth, so Flat Maps use various projections to represent a round earth.
• Globe properties
• All meridians are equal in length
• All meridians converge at the poles
• Lines of latitude are parallel to the equator and to each other
• Parallels decrease in length as one nears the poles
• Meridians and parallels intersect at right angles
• The scale on the surface of the globe is the same everywhere in all directions

Equal-Area or Equivalent Projections

• These maps show the actual areal extent of the earth’s surface. This distorts the shapes of the regions.

Conformal Projections

• True-shape projections which accurately portray the shapes of small areas.
• A map cannot be both conformal and equivalent (equal-area)

Equidistant Projections:

• Shows true distance from one or two central points. i.e. the map will show correct distance from point A to points B and C but not from point B to point C.
• A map cannot be both equidistant and equal-area!

Azimuthal Projections:

• Shows true direction from one central point to all other points.
• Azimuthal projections may also be equivalent, conformal, or equidistant

Map Scales

• Ratio between the distance between things on the map and the distance between the same things in the real world.
• Verbal Scale: 1” = 1 mile or 1cm = 5km
• Graphic scale: sometimes called a bar scale
• Representative Fraction Scale: 1:24,000
• Small Scale = very generalized (1:3,000,000)
• Large Scale = detailed (1:24,000)

Types of Maps

• Topographic Maps: depict the shape and elevation of the terrain.
• Show surface areas in relatively high detail
• Display both cultural and physical features
• Contour Lines: show elevation
• Contour Interval: the vertical spacing between lines
• Relief (elevation) also shown using:
• Spot Heights
• Benchmarks
• Shaded Relief
• Thematic Maps: used for data representation
• Point Symbols
• Area Symbols – more standard and may be symbols or colors
• Choropleth maps (use color to show data)
• Area Cartogram (Value-by-Area Map) – use size for data
• Line Symbols – used to represent features that have length but insignificant width (roads, political boundaries, rivers, etc…)
• Flow-Line Maps – used to portray linear movement

Remote Sensing

• Detecting the nature of an object without direct contact with that object. i.e. not walking over the ground to make a map.
• Aerial Photography
• mapping from the air, usually by plane.
• Orthophotomap
• an aerial map to which has been added supplementary information.
• False-Color Images
• photos produced using non-visible radiation.
• Other, Non-Photographic Images
• Thermal
• Radar Images
• Lidar

· Satellite Images

o Landsat Satellites are the standard U.S. imaging satellites

Geographic Information Systems (GIS)

· Computer based mapping systems which allow you to easily manipulate data to produce thematic maps. Using layers…

· Assemble, store, manipulate, analyze and display geographically referenced information

o Database of digitally recorded geographic information from variety of sources

o Computer displays any combination of data showing relationships among variables

o Used in all professions

Websites for Mapping

https://www.cia.gov/library/publications/the-world-factbook/

http://www.lib.utexas.edu/maps/world.html

http://www3.shastacollege.edu/dscollon/images/Figures,%20Diagrams%20and%20Maps.htm

http://www.reliefweb.int/rw/dbc.nsf/doc100?OpenForm

http://www.scotese.com/Default.htm (PaleoMaps)

http://maps.google.com/

http://earth.google.com

http://www.eduplace.com/ss/maps/

http://geology.com/

http://www.geometrie.tuwien.ac.at/karto/