GIS in Real Estate

GIS in Real Estate Phil Hurvitz CAUP-Urban Form Lab April 13, 2005

Overview • What is GIS? • How is GIS used outside of real estate • Data models used in GIS • Lab session_

Overview • What is GIS? • How is GIS used outside of real estate • Data models used in GIS • Lab session

What is GIS? • GIS is a computer-based technology used for the • Capture • Storage • Manipulation • Analysis, and • Display of spatially referenced data_

What the hell does that mean? • Anything you have ever seen, or could imagine on a map can be stored and analyzed with specialized software on a desktop PC • (Examples to follow)…_

Why use a GIS? • An extension of the paper map, but much more than a map, as you will see • GIS uses the analytical power of the computer to complete complex tasks • Computer's storage power to manage large data sets. • Integration of many different types of data from many different sources • GIS maps a variety of different data to the same coordinate space (allows for combination of data)_

What are the necessary parts to a GIS? • Trained personnel (the most expensive part) • Software (at the high end, ArcGIS, ~$25,000 per seat) • Data (many for free, some cost $$) • Computers (even a moderate desktop PC these days can perform dazzling things) • Ideas!_

GIS use examples in various disciplines • Natural resource management • Telecommunications • “Traveling salesman” problem • Risk management & emergency response • Space exploration • Urban form & Public Health

Natural resource management • Where are areas on a forest that meet a given complex set of criteria? • “What parts of the forest are located: • within 100 ft of a stream, • beyond 50 ft from a road, • on greater than 30% slope?”

closer than 100 ft to a stream, and farther than 50 ft from a road, on > 30% slope?

Telecommunications • Cellular phone towers

“Traveling salesman” problem

Space exploration

Urban form & Public Health • Urban sprawl and automobile dependence • decreased activity levels • increased obesity rates • Is urban spatial composition and configuration and indicator for obesity or other disease? • Can communities be structured to promote an increase in activity levels? • GIS is a central tool in quantifying the urban environment

Walkability & Bikeability Modeling • WBC Project, funded by CDCs • Urban Form Lab (Anne Moudon, Chanam Lee) • A GIS extension for obtaining environmental data in a household’s neighborhood • Urban features within walking/cycling distance • 200+ variables per household • Stat

Walkability & Bikeability Modeling

What is in the neighborhood? 1 km radius 3 banks 1 bar

How do land uses cluster?

Spatial Data Model: Basic Data Types • GIS are driven by spatial data • 2 basic spatial (coordinate/geometric) data models exist • vector: based on geometry of • points • lines • polygons • raster: based on geometry of • grid cells (images, bitmaps, DEMs)_

each point locationhas a record in thetable airports are point features each point is stored as a coordinate pair Vector Data Model Points: represent discrete point features

each road segmenthas a record in thetable roads are linear features Vector Data Model Lines: represent linear features

node node vertex vertex vertex vertex Vector Data Model Lines: fundamental spatial data model • Lines start and end at nodes • line #1 goes from node #2 to node #1 • Vertices determine shape of line • Nodes and vertices are stored as coordinate pairs_

each bounded polygonhas a record in thetable landforms and water are polygonal features Vector Data Model Polygons: represent bounded areas

Vector Data Model Polygons: fundamental spatial data model Polygon #2 is bounded by lines 1 & 2 Line 2 has polygon 1 on left and polygon 2 on right_

Vector Data Model Polygons: fundamental spatial data model complex data model, especially for larger data sets “arc-node topology,” only used for ArcInfo data sets_

digital orthophoto digital elevation model (DEM)_ Raster Data Model A few different types of raster data

Raster spatial data model • origin is set explicitly • cell size is always known • cell references (row/column locations)are known • cell values are referencedto row/column location • values represent numerical phenomena orindex codes for non-numerical phenomena_

Raster Data Model • Characteristics of the raster data model: • Rectangular grid of square cells • – Shape of discrete polygonal features generalized by cells • + Continuous (surface) data represented easily • + Simple data structure_

Raster Data Model • Raster data are good at representing continuous phenomena, e.g., • Wind speed • Elevation, slope, aspect • Chemical concentration • Likelihood of existence of a certain condition • Electromagnetic reflectance (photographic or satellite imagery)_

Relational Database Model & Attribute Data Structures • The “where” of GIS is determined by coordinate (map) data structures, but … • The “what” of GIS is determined by tabular (relational database) data structures • Thus, tabular data are just as important as coordinate data_

Relational Database Model & Attribute Data Structures • Attribute data are stored in database tables. • Tables are composed of: • fields and • records_

Relational Database Model & Attribute Data Structures • You may already be familiar with some types of relational databases • dBase • rBase • MS Access • MS Excel (database functionality) • Oracle, INFORMIX, INGRES, SQL Server • MySQL, PostgreSQL • INFO (in ArcInfo)_

Relational Database Model & Attribute Data Structures • Each vector data source has an attribute table

Relational Database Model & Attribute Data Structures • Tables can be linked and joined (“related”) by use of common values in fields

Relational Database Model & Attribute Data Structures • Relationship between tabular and map data • one-to-one between features and records • when a selection is made, both the record and feature are selected

Lab Session • Open GIS software • Download Seattle & King County data • Perform query & display • Create a map displaying a simple selection or analysis

GIS in Real Estate