Societal Issues (privacy, surveillance, ethics) e.g., Google StreetView Google Maps Mania Blog Early and late May 2008 More surveillance (electronic, video, biological, chemical) integrated into national system From Chris Peterson, Foresight Institute As presented at OSCON 2008, Portland Sewer monitoring has begun “The test doesn’t screen people directly but instead seeks out evidence of illicit drug abuse in drug residues and metabolites excreted in urine and flushed toward municipal sewage treatment plants.” From Chris Peterson, Foresight Institute As presented at OSCON 2008, Portland “Citizen Sensors” UCLA Center for Embedded Networked Sensing, http://peir.cens.ucla.edu Lecture 10 Geographic Databases Gateway to Spatial Analysis Definitions Database – an integrated set of attributes on a particular subject Geographic (=geospatial) database – set of attributes on a particular subject for a particular geographic area Database Management System (DBMS) – software to create, maintain and access databases cell towers +/- 500 m Google db of tower locations Wi-Fi +/- 30 m iPhone GPS +/- 10 m iPhone uses reference network db Graphic courtesy of Wired, Feb. 2009 Skyhook servers and db A GIS can answer the question: What is where? WHAT: Characteristics of features (= attributes). WHERE: In geographic space. A GIS links attribute and spatial data Attribute Data • Flat File or DBMS • Relationships • Topology Table Map Data • Point File • Line File • Area File • Topology Type Flat File or DBMS Attribute Attribute Attribute Record Value Value Value Record Value Value Value Record Value Value Value Types of DBMS Models Hierarchical Network Relational - RDBMS Object-oriented - OODBMS Object-relational - ORDBMS Historically, databases were structured hierarchically in flat files... Relational Databases rule now 2/1/98 2/4/98 Role of DBMS System Task Geographic Information System • • • • • Data loading Editing Visualization Mapping Analysis Database Management System • • • • Storage Indexing Security Query Data “Programmable API” Relational DBMS (1) Data stored as tuples (tup-el), conceptualized as tables Table – data about a class of objects Two-dimensional list (array) Rows = objects Columns = object states (properties, attributes) Table Row = object Vector feature Column = attribute Relational DBMS (2) Most popular type of DBMS Over 95% of data in DBMS is in RDBMS Commercial systems Microsoft Access Microsoft SQL Server Oracle IBM DB2 Informix Sybase Relational Join Fundamental query operation Occurs because Data created/maintained by different users, but integration needed for queries Table joins use common keys (column values) Table (attribute) join concept has been extended to geographic case Relational Databases 2/1/98 2/4/98 SQL Structured (Standard) Query Language – (pronounced SEQUEL) Developed by IBM in 1970s • Standard for accessing relational databases Three types of usage Stand alone queries High level programming Embedded in other applications Types of SQL Statements Data Definition Language (DDL) Create, alter and delete data CREATE TABLE, CREATE INDEX Data Manipulation Language (DML) Retrieve and manipulate data SELECT, UPDATE, DELETE, INSERT Data Control Languages (DCL) Control security of data GRANT, CREATE USER, DROP USER Spatial Query/Search & Retrieval: Gateway to Spatial Analysis Overlay is a spatial retrieval operation that is equivalent to an attribute join. Buffering is a spatial retrieval around points, lines, or areas based on distance. Overlay Image courtesy of K. Foote/M. Lynch, UT-Austin Overlay like an attribute join 2/1/98 2/4/98 Types of overlay operations Union Intersect Identity Max Min Etc. Union computes the geometric intersection of two polygon coverages. All polygons from both coverages will be split at their intersections and preserved in the output coverage. Union within 25 miles of a city OR within 25 miles of a major river. Intersect computes the geometric intersection of two coverages. Only those features in the area common to both coverages will be preserved in the output coverage. Intersect within 25 miles of a city AND within 25 miles of a major river. Identity computes the geometric intersection of two coverages. All features of the input coverage, as well as those features of the identity coverage that overlap the input coverage, are preserved in the output coverage. Identity Portion of the major city buffer WITHIN the major river buffer within 25 miles of a city OR within 25 miles of a major river. within 25 miles of a city AND within 25 miles of a major river. Intersect Identity Raster Retrieval: Map Algebra Raster overlay Combinations of spatial and attribute queries can build some complex and powerful GIS operations. Input Grid A Input Grid B Compared with Output Grid C Buffer Recode OR And many more …. See spatial analysis handout on course web site.