Geog 463GIS Workshop

April 17, 2006

Outlines

• Data Acquisition– Acquiring spatial data– Metadata– Spatial data quality– Determining fitness-for-use of data

• Spatial Data Infrastructure (SDI)– Concepts of SDI– What constitute SDI?– Nature/characteristics of SDI

Part I. Data Acquisition

Evaluating the applicability of data is one of essential skills for GIS professionals

Acquiring spatial data

• Use data download service– USGS National Map Seamless Data Distribution System

http://seamless.usgs.gov

– USGS EROS Data Center http://edcwww.cr.usgs.gov/

– Microsoft’s Terraserver http://terraserver.microsoft.com/

– TIGER/Line by Census Bureau or ESRI• http://www.census.gov/geo/www/tiger/tiger2002/tgr2002.html

• http://www.esri.com/data/download/census2000_tigerline/index.html

– Subnational GIS clearing house (e.g. WAGDA)…

• Use data catalogue service (or spatial portal)– Geospatial one-stop http://www.geodata.gov

– ESRI geographynetwork.com http://www.geographynetwork.com/

Tips for data acquisition

• By geographic scale– Data resolution is often related to the geographic scale of data

providing agency being considered – federal data sources have lower resolution with wider

geographic coverage (e.g. LU/LC in EROS Data Center)– parcel data can be found in the local level (e.g. City of Seattle)

• By related agency and organizations– Best data about housing can be found in HUD… – Best data about transportation can be found in BTS…– Best data about education can be found in NCES…– Best data about justice can be found in BJS…

• By theme– Talk to resource persons in the area; they probably have go

through data search processes

Also read http://courses.washington.edu/geog360a/dataatlibs2003.ppt if you’re not familiar with UW library system

Metadata

• Describes content and characteristics of data• Helps determine fitness for use

– Is the data suitable for the application?• Is metadata always available?

– No (much shared data is more likely to be published with metadata e.g. USGS public domain data)

• What if metadata is not available? – Look for data dictionary at least; or contact persons in

charge• Metadata standard for public data in the U.S.

– FGDC metadata content standard (www.fgdc.gov)

Reading FGDC metadata

Want to know…? Sections in FGDC metadata

Map scale or resolution Data Quality - Lineage

How current? Identification – Time Period

Which area is covered? Identification – Spatial Domain

How is data processed? Data Quality – Lineage

How accurate? Data Quality - Accuracy

Datum, map projection Spatial Reference

Data structure {vector, raster} Spatial Data Organization

Attributes Entity and Attribute

Never miss reading abstract and purpose!

Example: http://wa-node.gis.washington.edu/~uwlib/10mdem.html

Creating metadata

• How do I create metadata?– Use metadata creation/editing tool

• ArcCatalog from ESRI• tkme from

http://geology.usgs.gov/tools/metadata/tools/doc/tkme.html

• How do I check if this metadata conforms to FGDG Content Standard?– Use metadata validation tool

• Install program mp from http://geology.usgs.gov/tools/metadata/tools/doc/mp.html

• Use web service at http://geo-nsdi.er.usgs.gov/validate.php

Spatial data quality

where– Column: components of geographic information– Row: components of data quality 

• Accuracy: lack of discrepancy between measurement and values considered true (e.g. is this location near true value?)

• Consistency: whether given components conform to logical rules (e.g. any digitizing error?)

• Completeness: whether what’s required is encoded in data (i.e. anything missing)

 

  Space Time Attribute

Accuracy Positional accuracy   Attribute accuracy

Consistency Logical consistency  

Completeness Completeness   Completeness

FGDC metadata terms

How is spatial data quality related to fitness for use of data?

Determining fitness for use• Does map scale or resolution of the data provide the level of details

required by the application? – Using low-resolution satellite image for street-level survey is not

acceptable– Any generalization algorithms used?

• Is data current enough to support needs identified from P1?– Using outdated data for replacing a old map is not acceptable

• Are specific characteristics of data useful for the application?– Topology for routing operation– Multispectral image for land use detection– Non-planar representation for 3D visualization

• Any processing steps linked to usefulness of data for specific applications?– Some processing steps brought about irreversible effects on data (e.g.

unknown algorithm parameters)

*Questions shown in this lecture note are not intended to be exhaustive

Determining fitness for use

• Is the stated level of accuracy sufficient given error tolerance?– Requirements for accuracy vary highly by the applications– Required types of accuracy vary by need-to-know questions or

research questions (e.g. measuring parcel size require relative accuracy while surveying require absolute accuracy)

• Is the state level of completeness of features or attribute adequate to need-to-know question?– Some entities and attributes are required rather than optional

• Logical consistency of data?– Doesn’t data lack conformance to logical rules? (e.g. is identifier

generated properly? Doesn’t data has too many sliver?) – Does metadata indicate that the agency put any effort in quality

control? (e.g. lack of information in data quality section)

Part II. Spatial Data Infrastructure

Searching for the day we take less pain in data acquisition

GIS in the future

• Imagine the future when information is extracted from data upon request (maybe future is now)

• In the future, data is right there, and different data are integrated in a seamless manner so that value-added products can be generated in a timely fashion

• What are barriers to getting there? Are we getting there? What are steps towards making the best use of spatial data?

Role of geographic information

• Statistics shows that 80% of government-related activities require locational information

• Business demand exist to analyze customers’ need on a locational basis

• There are overriding concerns for understanding the complexity of human and natural environment and its interaction

• Sustainability has been widely acknowledged as a future agenda in varying organizational structures

Spatial data as commodity

• Spatial data infrastructure provides enabling environment for a spatially enabled society– Geographic information is widely used to support

decision-making• Seen as assets promoting

– good governance– economic development– improved environmental sustainability

• Seen as push towards information society • Access to applicable spatial data is essential to

this endeavor

Spatial data as infrastructure

• Airplane doesn’t fly, but airline does• Highway only doesn’t take you there, but all related

technical and institutional arrangements do• Spatial data only doesn’t meet your need, but multiple

aspects related to creation, maintenance, extraction, and dissemination of spatial data do

• See Figure 2.1 from the assigned reading (p. 24)• Due to its dynamic and incremental nature (user-driven

& successive developments of SDIs on top of the existing infrastructure), it is not straightforward to measure benefit

• SDIs provide enabling environment that facilitates communication

Integration of spatial data for sustainable development

• Locational framework can act as a glue that puts together related themes– Sustainability can be understood by examining relationships of all related themes, not

by examining one theme separate from other themes– Sustainability can be understood by examining connected geographic areas that reach

beyond a single jurisdiction (e.g. watershed analysis)

Thematic integration

Geographic integration

SDI as Societal GIS

• Remember the scope of GIS project

• The larger the scope of GIS project is, the more base data is shared, thus generating more benefit

• What about national or global effort to sharing spatial data? (e.g. NSDI, Global Map)

What constitute SDI?

• What is needed to facilitate data sharing? Or what are barriers to facilitating data sharing as a counterargument?– What if there’s no metadata that describes data?– What if there’s no people who know characteristics and

constraints of spatial data?– What if there’s no website for data dissemination? (e.g.

clearinghouse)– What if there’s no standards that promote interoperability (e.g.

FGDC metadata content standard, OLE, DCOM, http)?– What if there’s no coordination between agency?– What if there’s no willingness to share data?

• SDI = spatial data + people + technology + standards + policy

Relations between SDI components

People Data

Technology

Policy

Standards

From the assigned reading (p. 27)

Sustainable development

Decision support Good governance

Evolving SDI Concept

Past Present and future

Data creation Data use/sharing

Data provider Data user

Data availability Data applicability

Linkage of available databases

Management of information assets

Adapted from Rajabifard et al 2002

Evolution of data services

From The SDI Cookbook (2004)

Developing SDI

• Developing core data– Standards for framework or reference data

• Describing data: metadata– Metadata content standards (e.g. CSDGM)

• Discovering data: data catalogue– Standards for data clearinghouse (e.g. Z39.50)

• Accessing data: data access– Data exchange/format standards (e.g. SDTS)

• Processing data: data portrayal and processing– Web mapping, geoprocessing service (e.g. W3C)

From “The SDI Cookbook” V2 (2004)