GI Sciencespatial data modelling

Dr Nigel Trodd

Science and the Environment

Coventry University

Aim & objectives

To understand the process of building a digital representation of reality

• to characterise reality (as a spatial concept)• to identify the process of modelling geographical

phenomena• to identify & exemplify entitation & data modelling• to identify vector and raster data & their data

structures

Building GI models

I am a Geographer

I model places & spatial phenomena

I am a Computer Scientist

I model information in a database

GI Science = Geography + Computer Science

How can we store geographical data in a computer?

the real world is complexandcomputers are very simpleandcomputers need us to model the geography for them.

How do we model the real world in a computing environment ?

from reality to spatial data structures

in

1.. 2.. 3.. 4 (easy) steps

1. from reality to geographical phenomena

2. from geographical phenomena

to spatial entities

3. from spatial entities

to spatial data models

4. from spatial data models

to spatial data structures

1. from reality to geographical phenomena

2. from geographical phenomena

to spatial entities

3. from spatial entities

to spatial data models

4. from spatial data models

to spatial data structures

terminology overload...

... there’s more

How do we view reality?

1. from reality to geographical phenomena

Values at different places• Continuous variation – biomass, elevation, SST

Points and edges with associated data• Discrete objects - house, pipeline, river,

coastline

1. from reality to geographical phenomena

2. from geographical phenomena to

spatial entities

the famous 5ive...pointslinesareas

networks & surfaces

Geometry

Topology

Concepts of geography

3. from spatial entities

to spatial data models

object-based

field(or layer)-based

wakey wakey

… here comes the

easy bit

vector & raster

4. from spatial data models

to spatial data structures

I am NOT a Geographer

I am NOT a Computing Scientist

I am a GI Scientist.

I model.

I am crude.

I use basic IT.

I work.

Summary

I am a GI Scientist. Are you?

• outline the art of building a digital

representation of reality.

• identify & exemplify 5 spatial entity types.

• explain the elements of a spatial data model.

• identify differences between vector and

raster data & exemplify their data structures.