Dr Nigel TroddCoventry University

Sourcing Geodata

giservices require

peoplesoftware

data

method

hardware

geospatial data consist of

geographical entitiesattributesmetadata

geospatial data are useful only if

available & accessiblefit for purpose

referenced to a common spatial referencing system

Aim & objectives

To identify & understand the process of building a geospatial database

We willidentify sources of geographically referenced data exemplify techniques to acquire geospatial data

importance of data acquisition

constrains data analysisinfluences output quality

determines economic viability50% of the total cost & 70% - 80% of the time of a GIS project

revolve around data acquisition

…the cost of data

10 seats 100 seats

$ % $ %

Hardware 30 3.4 250 8.6

Software 25 2.8 200 6.9

Data 400 44.7 450 15.5

Staff 440 49.1 2000 69.9

Total 895 100 2900 100Source: Longley et al. 2001

a system to

the data stream in GIS

capturestorecheckintegratemanipulate analysedisplay spatial data

capturestorecheckintegratemanipulate analysedisplay spatial data

sourcing data

Determine location Georeferencing system

Determine extent of phenomena from reality to spatial data

structures

Characterise properties of phenomena

data sourcesPrimary data sources

Field survey Questionnaires Aerial photos & satellite images

Secondary data sources Maps & other published documents Government databases e.g. health, crime,

social security, land registry Private sector databases e.g. credit rating,

lifestyle (EPOS)

primary data sourcesField survey

Satellite Navigation System

GPS & GLONASS principles

Limitations

Working environment

Selective availability

Range uncertaintyData quality

SA on SA off DGPS

Horizontal

100m 10-20m <1-5m

Vertical 160m

GPS applications

remote sensing …the acquisition of physical data of an object without touch or

contact (Lintz & Simonett 1976)

Earth observation by remote sensing

IKONOS 1m-sharpened multispectral image

Poppy fields in Kandahar, Afghanistan

Image courtesy of United Nations Office on Drugs Crime

… to local

Global…

Change detection: deforestation & fragmentation in the Amazon

1975 1986 1992

secondary data sources

digitising

& scanning

butCartographic licence and Data Currency

Map-1978 Imagery-1997

Government organisations with GB geodata holdings

Ordnance Survey GB & Ordnance Survey Northern Ireland Topographical & grid references

HM Land Registry Land ownership & house prices

Highways Agency Traffic flow

Post Office Postcode

Environment Agency Flood

British Geological Survey Geological & geomagnetic

UK Met Office & European Centre fir Medium-Range Weather Forecasting

Weather & climate

Natural Environment Research Council Environmental

Forestry Commission Vegetation

National Park Authorities Biodiversity & visitors

Office for National Statistics Demographic

National Health Service Patient & estates

Higher Education Statistics Authority Student

UK Passport Service Travellers

English & Scottish Heritage Historical

The National Archives Genealogical

The Countryside Agency Rural

Police Authorities Crime

Central Office of Information Government

Local Government Address & demographic

Home Office Identity card

Geocoded socio-economic survey

uk census

Population census

• every 10 years since 1801 except 1941

• target resources & plan service provision

uk census 2001

2001 census held on Sunday 29 April 2001

• £255 million operation organised by Office for National Statistics, General Register Office for Scotland and Northern Ireland Statistics & Research Agency

• Population, Health, Housing, Employment, Transport, Ethnic Group

• Legal obligation to complete a census form but identification of individuals protected for 100 years by Census Confidentiality Act 1991

butOrdnance Survey +

British Geological Survey +

ONS Census +

National LANDMAP satellite imagery

= 1% of total UK digital data volume

… and the rest?

… and what about 'soft' data?

soft data

Communities – assets, land useIndividuals e.g. farmers, preferences & fearPrivate companies e.g. Rail Track, ExperianMultimedia e.g. photos, video, text, oral testimony