Winter 2011 GIS Institute Space: Questions & Tools

First Off: Introductions Take a minute or two to introduce: – Yourself – Your research (or project) – Why you’re taking part in the Institute – What you hope to gain – Fears? Winter 2011 GIS Institute

Space: Questions Questions can range from basic to complex : – How does a variable or phenomenon vary over space? (Can be answered with a map) – How does distance to public transportation affect house values? (Can be answered using traditional statistical software, with spatial variables created using GIS) – What is the spatial distribution of foreclosures in Phoenix, AZ? (Can be answered with maps and descriptive spatial statistics) – What is the impact of foreclosure densities on neighborhood crime? (Can be answered with spatial statistics and models) Winter 2011 GIS Institute

Space: Tools As with any other discipline, geographers work with a range of “spatial” questions, and there are generally myriad approaches with which to answer those questions This week we will focus primarily on developing your comfort level with GIS, G eographic I nformation S ystems – Commonly used for data collection, management, mapping, and analysis Winter 2011 GIS Institute

What is GIS? G eographic I nformation S ystems or S cience – A bringing together of skills, theory, computer science, database management, and geography – A collection of: Hardware Software Data People Procedures Network – An abstraction of reality Rachel Franklin

Clarke (2001) presents the following definitions: GIS is “a powerful set of tools for storing and retrieving at will, transforming and displaying spatial data from the real world for a particular set of purposes.” – Burrough, 1986 Rachel Franklin

GISs are “ automated systems for the capture, storage, retrieval, analysis, and display of spatial data.” – Clarke, 1995 Rachel Franklin

A GIS is “an information system that is designed to work with data referenced by spatial or geographic coordinates. In other words, a GIS is both a database system with specific capabilities for spatially-referenced data, as well as a set of operations for working with the data.” – Star and Estes, 1990 Rachel Franklin

GIS is “a special case of information systems where the database consists of observations on spatially distributed features, activities, or events, which are definable in space as points, lines, or areas. A geographic information system manipulates data about these points, lines, and areas to retrieve data for ad hoc queries and analyses.” – Dueker, 1979 Rachel Franklin

GIScience is “the generic issues that surround the use of GIS technology, impede its successful implementation, or emerge from an understanding of its potential capabilities.” - Goodchild, 1992 Rachel Franklin

Source: sutton.gov.uk Source: krygier.owu.edu

Roles of a GIS (Fotheringham) Data manipulation Data integration – Using GIS to create new information that is then used in other software or analysis environments Data visualization – For example, looking at regression residuals Winter 2011 GIS Institute

A brief history of GIS Cartography, especially thematic maps Map overlay – Tyrwhitt’s 1950 chapter in Town and Country Planning Textbook – McHarg’s 1969 Design with Nature Source: architectmagazine.com

Brief History Continued… The Canada Geographic Information System, mid-1960s The Census Bureau’s DIME (Dual Independent Map Encoding), late 1960s Computerized cartography Freestanding GIS software packages Ever-increasing computer power Ever-increasing quantities of spatial data Rachel Franklin

What can we do with a GIS? Make maps Compute summary statistics Import, manipulate, and manage data Spatial analysis Rachel Franklin

Early example of spatial analysis: John Snow’s 1854 Cholera Map

Other Examples Habitat suitability Hurricane vulnerability Heat wave vulnerability Bus stop locations Smart growth policies Rachel Franklin

Nice Maps

Winter 2011 GIS Institute

Interactive Maps

Rachel Franklin

What do you think of this map? The analysis? Rachel Franklin

Or this one? (Hint: sometimes our spatial research challenges in aren’t necessarily cartographical)

Traditional Spatial Analysis, Redux Winter 2011 GIS Institute Tobler’s First Law of Geography states that, “ Everything is related to everything else, but near things are more related than distant things. ” Geographers and others have often try to measure the “ everything is related to everything else ” by looking at connections between pairs of locations or entities – Provides clues about diffusion behaviors, as well as strength of ties between places – e.g. migration flows, commuter flows, communication flows

Regionalization MIT’s SENSEABLE City Lab used telephone call data from British Telecom to redraw the regional map of Great Britain. Winter 2011 GIS Institute

Traditional Spatial Analysis, Redux Winter 2011 GIS Institute

Organizing Spatial Data in a GIS A GIS doesn’t save information as maps – Rather, we tell the GIS how to locate objects in relation to other objects and in space Things to be aware of: – Your spatial data model – The relationships your objects have with each other in the real world e.g. street intersections or shared state borders We call this “topology” Winter 2011 GIS Institute

Spatial Data Models Most common are vector and raster Winter 2011 GIS Institute VectorRaster Polygon Point Line

Vector Model Features are stored as points, lines or polygons – All are combinations of nodes and vertices Locations are recorded as X,Y coordinates Each feature – point, line, or polygon – is linked to an “ attribute table ” or set of variables – For example, you could have a dataset of cities, represented as points, and the attribute table might contain characteristics of the city – population, median household income, etc. Feature classes – or datasets of spatial objects – contain only the same types of objects – This means only points or lines or polygons – And since they all share the same attribute table, they should be the same thing So, no combining cities and septic systems in one feature class, even though both might be points Winter 2011 GIS Institute

Why We Like the Vector Model Features can be located precisely We can store lots of information (variables or attributes) about each feature Useful for many types of map-making Perfect for types of analysis, such as areas, lengths, or connections Winter 2011 GIS Institute

Raster Data Model Sub-divides a study area into square pixels – rows and columns Only need the location of the upper left- hand corner and all other locations are implicit, assuming you know your pixel size Only one value is recorded for each pixel – For example, temperature, precipitation, or land use type Winter 2011 GIS Institute

Why We Like the Raster Model Best for continuous data Analysis can sometimes be faster And some types of analysis require raster data “Yes, raster is faster, but raster is vaster, and vector just seems more correcter.” – Dana Tomlin Winter 2011 GIS Institute

Topology – Modeling Feature Behavior Topology sets the rules of behavior for features in a feature class A classic example is road networks: Basic topology rules deal with adjacency, connectivity, overlap, and intersection Winter 2011 GIS Institute Highway OverpassTypical Street Corner

The End…for Now… Let’s go see the computer lab And break for lunch We’ll reconvene at 1:00 pm in CIT 265 Winter 2011 GIS Institute