Unit I - Maps

Cartography Cartography – science of map- making Cartography – science of map- making Cartographers must choose: Cartographers must choose: Types of projectionsTypes of projections Levels of simplificationLevels of simplification Levels of aggregationLevels of aggregation Map scaleMap scale Symbols to useSymbols to use

Maps All maps are created by projecting the earth’s 3D shape, which in reality is a bumpy oblate spheroid or geoid, onto a 2D surface. All maps are created by projecting the earth’s 3D shape, which in reality is a bumpy oblate spheroid or geoid, onto a 2D surface. 3D shapes can never truly be 2D 3D shapes can never truly be 2D All flat maps have some distortion in their representation of distance, shape, area, or direction. All flat maps have some distortion in their representation of distance, shape, area, or direction.

Map Projections There are many possible map projections. There are many possible map projections. A cartographer must choose the one which will best represent their purpose for the map. A cartographer must choose the one which will best represent their purpose for the map. No best projection – the one chosen depends on the data they wish to represent. No best projection – the one chosen depends on the data they wish to represent.

Mercator Projection Preserves compass direction, distorts the area of landmasses relative to each other (higher latitudes – larger in size) Preserves compass direction, distorts the area of landmasses relative to each other (higher latitudes – larger in size)

Fuller Projection Maintains the accurate size and shape of landmasses but completely rearranges direction, so that the cardinal directions no longer have any meaning Maintains the accurate size and shape of landmasses but completely rearranges direction, so that the cardinal directions no longer have any meaning

Robinson Projection Provides an aesthetically pleasing balance (does not maintain accurate area, shape, distance, or direction…but minimizes errors) Provides an aesthetically pleasing balance (does not maintain accurate area, shape, distance, or direction…but minimizes errors)

Azimuthal Projection Either the North or South pole is at the center of the map Either the North or South pole is at the center of the map

Level of Simplification Refers to the level of detail included Refers to the level of detail included What cartographers choose to display on the map depends on the overall purpose of the map and the size of the area covered What cartographers choose to display on the map depends on the overall purpose of the map and the size of the area covered

Level of Aggregation Refers to the size of the unit under investigation such as cities, counties, states, or countries Refers to the size of the unit under investigation such as cities, counties, states, or countries Depends on the purpose of the map Depends on the purpose of the map

Scale Refers to ratio between the distance on a map and the actual distance on the earth’s surface Refers to ratio between the distance on a map and the actual distance on the earth’s surface Small-scale: the ratio between map units and ground units is small (usually for large areas) Small-scale: the ratio between map units and ground units is small (usually for large areas) Large-scale: cover much smaller regions Large-scale: cover much smaller regions

Resolution Refers to a map’s smallest discernable unit – smallest thing you see on a map. Refers to a map’s smallest discernable unit – smallest thing you see on a map.

Map Categories 2 categories: 2 categories: Reference maps: work well for locating and navigating between places.Reference maps: work well for locating and navigating between places. Thematic maps: display one or more variables across a specific space.Thematic maps: display one or more variables across a specific space.

Symbols Isoline (contour): lines that represent quantities of equal value and are familiar to those who use topographic maps for navigation – also used to represent values (population density). Isoline (contour): lines that represent quantities of equal value and are familiar to those who use topographic maps for navigation – also used to represent values (population density). Proportional symbols: the size of the chosen symbol – such as a circle or triangle – indicates the relative magnitude of some value for a given geographic region. Proportional symbols: the size of the chosen symbol – such as a circle or triangle – indicates the relative magnitude of some value for a given geographic region.

Type of Maps Location charts: convey a large amount of information by associating charts with specific mapped locations. Location charts: convey a large amount of information by associating charts with specific mapped locations. Dot maps: use points to show the precise locations of specific observations or occurrences (crime, births). Dot maps: use points to show the precise locations of specific observations or occurrences (crime, births). Example of Dot Map

Type of Maps Cont. Choropleth maps: use colors or tonal to represent categories of data for given geographic areas. Choropleth maps: use colors or tonal to represent categories of data for given geographic areas. Cartograms: transform space, such that the political unit – a state, country, with the greatest value of some type of data is represented by the largest relative area. Cartograms: transform space, such that the political unit – a state, country, with the greatest value of some type of data is represented by the largest relative area. Example of Choropleth Map

Visualizations Another interesting class of maps – become increasingly popular in recent years. Another interesting class of maps – become increasingly popular in recent years. Use sophisticated software to create dynamic computer maps, some of which are 3-D or interactive. Use sophisticated software to create dynamic computer maps, some of which are 3-D or interactive.

Cognitive “Mental” Maps An individual’s internal, geographic understanding of a place. An individual’s internal, geographic understanding of a place. Formed when people perceive information about their surroundings and then process that information into a mental image that reflects both the physical environment and that individual’s social, cultural, and psychological framework. Formed when people perceive information about their surroundings and then process that information into a mental image that reflects both the physical environment and that individual’s social, cultural, and psychological framework. May include hazards – items/places a person avoids during their daily routine. May include hazards – items/places a person avoids during their daily routine.

Preference Maps Show people’s ideas about the environmental, social, or economic quality of life in various places. Show people’s ideas about the environmental, social, or economic quality of life in various places.

Location/Distance Geographers use these to establish location and distance: Coordinate systemCoordinate system Absolute locationAbsolute location Longitude and latitudeLongitude and latitude Meridians – Prime MeridianMeridians – Prime Meridian International Date LineInternational Date Line Parallels Site Situation – Relative location Absolute distance Relative distance Connectivity Time-Space Convergence