Geographic Information Systems
Spatial Data

Mark Foley
mark.foley@dit.ie

Learning outcomes

Introduction

Data sources

The Fundamental Problem

Discrete Objects and Continuous Fields

Discrete Objects

Continuous Fields

Spatial entities - Vector

Raster

Raster representation. Each colour represents a different value of a nominal-scale field denoting land cover class.

Raster representation. Each colour represents a different value of a nominal-scale field denoting land cover class.

Maps and their influence
on the character of spatial data

Scale

Ratio of distance on the map to distance on the groundLarge scale => small area & vice versa

Ratio of distance on the map to distance on the ground
Large scale => small area & vice versa

Generalization issues

Projections

Distortions

Cylindrical Projections

Conic Projections

The “Unprojected” Projection

Projections:
(a) cylindrical, (b) azimuthal, (c) conic

Commonly used projections

Transverse Mercator

Irish Grid