Spatial Patterns & Information Selection (College Board AP® Human Geography): Revision Note

Spatial patterns

• Spatial pattern refers to the distribution of phenomena such as settlements across a geographical area

Location

• Location is one of the five themes of human geography and refers to where something is found on the earth’s surface

  • Absolute Location refers to the exact location of a place

  • This is expressed using either:

    • latitude and longitude

      OR

    • the Cartesian Coordinate System (X and Y axis)

  • Relative Location describes a place in relation to other places and can change based on context

• Absolute location is read off a grid system laid over the map

  • The graticule is the grid of latitude and longitude lines on a globe or world map

  • Lines of latitude, or parallels, run east–west and measure degrees north or south of the equator

  • Lines of longitude, or meridians, run north–south and measure degrees east or west of the prime meridian

• A grid reference is always given as latitude first, then longitude

  • For example, New Orleans is at roughly 30°N, 90°W

• Local and street maps often use a simpler alphanumeric grid instead

  • Columns are lettered and rows are numbered, so a feature can be located in square B4

Direction

• Direction describes where things are in relation to each other

  • Absolute direction refers to cardinal directions, which do not change based on perspective

  • Relative direction is based on an individual’s perception or context. “Ahead,” “left,” and “behind you” are examples of relative direction

Distance

• Distance measures how close together or far away things are to one another

  • Absolute distance measures the exact distance between two places and is given in standardized terms, such as kilometers, miles, or feet

  • Relative distance measures the perception of distance and generally takes into account things like time, money, or effort required to travel from one place to another

Elevation

• Elevation is the height of a point on the earth's surface above or below sea level

  • It is measured against mean sea level, usually in feet or meters

• Elevation is shown on a map using contour lines, which join points of equal height

  • Contour lines drawn close together show a steep slope

  • Contour lines drawn far apart show a gentle slope

• Elevation shapes human geography because it affects:

  • Climate — temperature falls as altitude rises, which shortens growing seasons and limits which crops will grow

  • Settlement — people cluster in lower valleys, basins and coastal plains rather than on steep upper slopes

  • Accessibility — mountainous terrain raises the cost of building roads and railways, which restricts trade

• For example, in the Andes most large settlements sit in high valleys and basins, with far fewer people on the steep slopes above them

Describing spatial patterns on a map

• Geographers use a set of standard terms to describe the distribution a map shows:

  • Clustered — features are grouped closely together

  • Dispersed — features are spread out, with space between them

  • Linear — features follow a straight line

  • Grid — features form a geometric arrangement at right angles

• These four terms are defined in full, with a diagram, in What are Spatial Concepts?re Spatial Concepts? (opens in a new tab)

• A strong description of a spatial pattern does three things:

  • Names the pattern, using one of the terms above

  • Gives direction, using cardinal directions such as north or southeast

  • Comments on density, saying where values are higher and where they are lower

• For example, on a choropleth map of US population density:

  • The pattern is clustered

  • The highest densities are in the northeast and along the west coast

  • Densities are lowest through the interior west

Time-space compression

• Time−space Compression describes the phenomenon in which the distance between places seems reduced due to improvements in technology

• Developed by David Harvey in 1990

  • Time−space compression plays an important role in globalization by making connections between people, ideas, and economies faster

  • Time−space compression works against the friction of distance, also known as distance decay

• Time−space compression counteracts the two closely related phenomena of friction of distance and distance decay

  • Friction of distance means that distance and interaction are inversely related

    • The further two people or places are from one another, the less interaction they will have

  • Distance decay refers to the lessening influence of something the further from its source you travel

    • Radio waves become weaker the further away from the tower the radio is situated

    • Modern technologies, including plane travel and the internet, have lessened the effects of distance decay

Information selection

• Map projections take the spherical shape of the earth and display it on a flat surface

• Because map projections place the globe onto a two-dimensional surface, cartographers must deal with the problem of distortions:

  • Shapes of continents or countries can be distorted

  • Distance between two points can increase or decrease

  • Relative size may be altered, and areas can appear much larger than they are

  • Direction can be distorted

• Every projection distorts the globe in some way, and each one distorts it differently

• Projections are grouped into three main forms, based on the shape used to transfer the globe onto a flat surface:

  • Cylindrical — the globe is projected onto a cylinder wrapped around it

  • Conic — the globe is projected onto a cone placed over it

  • Azimuthal, also called planar — the globe is projected onto a flat plane touching it at a single point

• Named projections belong to these forms:

  • Mercator and Gall-Peters are both cylindrical projections

  • A polar azimuthal map is an azimuthal projection centered on the North or South Pole

• A few projections are compromise projections, which do not belong to any one form

  • Robinson is a compromise projection — it reduces every kind of distortion a little, rather than preserving any single property exactly

Mercator maps

• Mercator maps are characterized by the following: 

  • Latitude and longitude are shown at right angles

  • Shapes of land masses are preserved, but size is distorted at the poles

  • They are most commonly used for navigation because they display lines of constant compass-bearing

  • They distort the relative size of continents

    • This is often seen by geographers as reproducing certain racist or ethnonationalist ideas

Gall-Peters projection map

• Gall-Peters Projection map preserves the correct relative size of landmasses but distorts the shape

Conic projections

• Conic projections show the earth’s surface in the form of a cone

  • Conic maps are useful for correct navigation in landmasses that primarily run east-west, such as the United States or China

Robinson map projections

• Robinson map projections preserve the size and shape of landmasses but distort polar areas

  • Robinson maps are generally more “correct” in terms of shape and size

  • However, because the lines of latitude and longitude are not constant, it is not useful for navigation

Azimuthal map

• Azimuthal projections project part of the globe onto a flat plane that touches the globe at a single point

• They show true direction from that central point to anywhere else on the map

  • This makes them useful for air and sea navigation, and for plotting flight paths

• Distortion increases with distance from the central point

  • Land near the edge of the map is stretched, and its shape and size are distorted

• A polar azimuthal map is centered on the North or South Pole

  • These are commonly used to show polar flight routes, sea ice extent, and Arctic territorial claims

[INSERT IMAGE — azimuthal projection]
Image caption: Azimuthal projection

Map scale

• Map scale is the relationship between a distance on the map and the same distance in the real world

• Scale can be shown in three ways:

  • A ratio, also called a representative fraction, such as 1:50,000

  • A written statement, such as "one inch represents one mile"

  • A bar scale, a marked line the reader measures a distance against

• Scale controls how much information a cartographer is able to include:

  • A large-scale map covers a small area in a lot of detail, so it can show individual streets and buildings

  • A small-scale map covers a large area in much less detail, so features have to be simplified or left out altogether

• Deciding what to keep and what to leave out at a given scale is called generalization

  • This is why two maps of the same place can show very different things

• Large-scale and small-scale maps are covered in more depth in Scales of Analysis, Patterns & Processes