EG1106 Geographic Information: a primer Mark Cresswell: Room E449b 15th October 2004 Maps & Representation

What is a map? How do maps provide information? Map Abstraction and Generalisation Using maps to communicate GIS 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 B A C D N

How do maps provide information? Consider the usefulness of this map B A 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: will have only a quarter of the space available for portraying information about a region than a map at a scale of 1: Map Abstraction and Generalisation

ABSTRACTION - This is the process whereby complex features such as drainage channels, road networks and buildings are reduced to: Lines the thickness of which may not be related to reality Symbols a 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

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 & E2 2 – 3:30 pm In room L106 (Loxford)

PRACTICAL IN 2 WEEKS (29 th Oct ) Groups A2, B1 and B2 2 – 3:30 pm Groups A1, C1 and C2 3:30 – 5 pm In room L106 (Loxford)