EG1106Geographic Information: a primer

Mark Cresswell: Room E449b

15th October 2004

Maps & Representation

What is a map?How do maps provide information?Map Abstraction and GeneralisationUsing maps to communicateGIS

Practical Today and IN TWO WEEKS

TOPICS

Maps convey information about a place by graphical (or tactile) means

Use of lines, points, symbols, shading and contours convey essential elements about a place.

Every map has a spatial frame of reference - such as gridlines (Ordnance Survey for example), geographical co-ordinates (latitude & longitude) or more localised (postcode or political wards)

Maps rely on a simplification of reality

What is a map?

Is this a map?

What is a map?

Is this a map?

What is a map?

North America

Central America

South America

Western and Central

Europe

Africa

Eastern Europe

Asia

Australia and New Zealand

Is this a map?

What is a map?

Do all maps have to faithfully replicate even gross features of reality - or can they be exploited to communicate concepts?

What is a map?

The map of the London Underground was originally drawn in the 1920s by Beck who was an electronics draughtsman

The Tube map is easily understood by everyone who uses it - but it bears little relation to the “real” railway network layout.

How do maps provide information?

Scale and Representation

All conventional maps have a SCALE - this tells the user how the features on the map relate spatially to the world it depicts.

Without a scale, maps do not inform the user of key information such as DISTANCE and SIZE.

How do maps provide information?Consider the usefulness of this map

BA

C

D

N

How do maps provide information?Consider the usefulness of this map

BA

C

D

N

100 miles

How do maps provide information?Symbols and colours

All maps show a simplification of reality

Complex real-world features are deconstructed and projected onto a 2-dimensional spatial reference system

Major features become a collection of lines, points, polygons and symbols

Cartographers will take an aerial photograph and produce a map retaining the essential elements - but without the complexity and unimportant information

Map Abstraction and Generalisation

GENERALISATION - varies the quantity of detail according to the scale.A map at a scale of 1:100 000 will have only a quarter of the space available for portraying information about a region than a map at a scale of 1:25 000

Map Abstraction and Generalisation

ABSTRACTION - This is the process whereby complex features such as drainage channels, road networks and buildings are reduced to:

Linesthe thickness of which may not be related to reality

Symbolsa church or hospital will have a standard symbol regardless of the size of the hospital or religious denomination of the church

Map Abstraction and Generalisation

A map does not have to be a road atlas or A to Z format of publication

Maps can be used to display any data that has a spatial (geographic) component.

We can show a map of a region or country and graphically show data in the form of colours and/or symbol size. These are CHLOROPLETH maps.

Using Maps to Communicate

Using Maps to Communicate

Ocean

Projected population in 20000.2 M - 16.4 M16.4 M - 48.5 M48.5 M - 107.5 M107.5 M - 270.1 M270.1 M - 1304.5 MNo Data

6000 0 6000 12000 Miles

N

EW

S

World

Using Maps to Communicate

Ocean

Life Expectancy39.8 - 49.549.5 - 5959 - 67.567.5 - 7373 - 79.3No Data

6000 0 6000 12000 Miles

N

EW

S

World

Using Maps to Communicate

GIS

Geographical Information System

Based around computer software

Maps become DYNAMIC – they can be updated as often as the information changes

Maps can be carried on digital devices – handheld computers with high resolution screens – updateable in real-time.

GIS

PRACTICAL TODAY

Groups D1, D2, E1 & E22 – 3:30 pm

In room

L106 (Loxford)

PRACTICAL IN 2 WEEKS (29th Oct)

Groups A2, B1 and B2

2 – 3:30 pm

Groups A1, C1 and C23:30 – 5 pm

In room L106 (Loxford)