Unit I - MapsUnit I - Maps

CartographyCartography

Cartography – science of map-Cartography – science of map-makingmaking

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

MapsMaps

All maps are created by projecting All maps are created by projecting the earththe earth’’s 3D shape, which in reality s 3D shape, which in reality is a bumpy oblate spheroid or geoid, is a bumpy oblate spheroid or geoid, onto a 2D surface.onto a 2D surface.

3D shapes can never truly be 2D3D shapes can never truly be 2D All flat maps have some distortion in All flat maps have some distortion in

their representation of distance, their representation of distance, shape, area, or direction.shape, area, or direction.

Map ProjectionsMap Projections

There are many possible map There are many possible map projections. projections.

A cartographer must choose the one A cartographer must choose the one which will best represent their which will best represent their purpose for the map.purpose for the map.

No best projection – the one chosen No best projection – the one chosen depends on the data they wish to depends on the data they wish to represent.represent.

Mercator ProjectionMercator Projection

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

Fuller ProjectionFuller Projection

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

Robinson ProjectionRobinson Projection

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

Azimuthal ProjectionAzimuthal Projection

Either the North or South pole is at the Either the North or South pole is at the center of the mapcenter of the map

Level of SimplificationLevel of Simplification

Refers to the level of detail includedRefers to the level of detail included What cartographers choose to What cartographers choose to

display on the map depends on the display on the map depends on the overall purpose of the map and the overall purpose of the map and the size of the area coveredsize of the area covered

Level of AggregationLevel of Aggregation

Refers to the size of the unit under Refers to the size of the unit under investigation such as cities, counties, investigation such as cities, counties, states, or countriesstates, or countries

Depends on the purpose of the mapDepends on the purpose of the map

ScaleScale Refers to ratio Refers to ratio

between the distance between the distance on a map and the on a map and the actual distance on the actual distance on the earthearth’’s surfaces surface

Small-scale: the ratio Small-scale: the ratio between map units between map units and ground units is and ground units is small (usually for large small (usually for large areas)areas)

Large-scale: cover Large-scale: cover much smaller regionsmuch smaller regions

ResolutionResolution

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

Map CategoriesMap Categories

2 categories:2 categories:• Reference maps: Reference maps:

work well for work well for locating and locating and navigating between navigating between places.places.

• Thematic maps: Thematic maps: display one or more display one or more variables across a variables across a specific space.specific space.

SymbolsSymbols Isoline (contour): lines Isoline (contour): lines

that represent that represent quantities of equal quantities of equal value and are familiar value and are familiar to those who use to those who use topographic maps for topographic maps for navigation – also used navigation – also used to represent values to represent values (population density).(population density).

Proportional symbols: Proportional symbols: the size of the chosen the size of the chosen symbol – such as a symbol – such as a circle or triangle – circle or triangle – indicates the relative indicates the relative magnitude of some magnitude of some value for a given value for a given geographic region.geographic region.

Type of MapsType of Maps Location charts: Location charts:

convey a large convey a large amount of information amount of information by associating charts by associating charts with specific mapped with specific mapped locations.locations.

Dot maps: use points Dot maps: use points to show the precise to show the precise locations of specific locations of specific observations or observations or occurrences (crime, occurrences (crime, births).births).

Example of Dot Map

Type of Maps Cont.Type of Maps Cont.

Choropleth maps: use colors or tonal to represent Choropleth maps: use colors or tonal to represent categories of data for given geographic areas.categories of data for given geographic areas.

Cartograms: transform space, such that the political unit – Cartograms: transform space, such that the political unit – a state, country, with the greatest value of some type of a state, country, with the greatest value of some type of data is represented by the largest relative area.data is represented by the largest relative area.

Example of Choropleth Map

VisualizationsVisualizations

Another interesting class of maps – Another interesting class of maps – become increasingly popular in become increasingly popular in recent years.recent years.

Use sophisticated software to create Use sophisticated software to create dynamic computer maps, some of dynamic computer maps, some of which are 3-D or interactive.which are 3-D or interactive.

Cognitive Cognitive ““MentalMental”” Maps Maps

An individualAn individual’’s internal, geographic s internal, geographic understanding of a place.understanding of a place.

Formed when people perceive information Formed when people perceive information about their surroundings and then process about their surroundings and then process that information into a mental image that that information into a mental image that reflects both the physical environment and reflects both the physical environment and that individualthat individual’’s social, cultural, and s social, cultural, and psychological framework.psychological framework.

May include hazards – items/places a May include hazards – items/places a person avoids during their daily routine.person avoids during their daily routine.

Preference MapsPreference Maps

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

Location/DistanceLocation/DistanceGeographers use these to establish location and Geographers use these to establish location and

distance:distance:• Coordinate systemCoordinate system• Absolute locationAbsolute location• Longitude and Longitude and

latitudelatitude• Meridians – Prime Meridians – Prime

MeridianMeridian• International Date International Date

LineLine

• ParallelsParallels• SiteSite• Situation – Relative Situation – Relative

locationlocation• Absolute distanceAbsolute distance• Relative distanceRelative distance• ConnectivityConnectivity• Time-Space Time-Space

ConvergenceConvergence