Massachusetts Institute of Technology Department of Urban Studies and Planning 11.520: A Workshop on Geographic Information Systems 11.188: Urban Planning and Social Science Laboratory GIS Principles & Methods September 14, 2005, Joseph Ferreira, Jr. (including contributions from Visiting Prof. Zhong-Ren Peng who taught the Fall 2003 class) Administrative notes regarding lab exercises and schedule • Lab Exercises #2: we've made some minor edits regarding how to control the labeling (it's different in new version, ArcGIS 9.1) • Lab Exercise grading o we aren't going to grade every detail o you'll get a 'check' = okay, 'check-plus' = especially good, or 'check-minus' = not as complete as we had hoped. o all together, the lab exercises count for 25% of semester grade. • Lab Exercise purpose: o quick start with basic ArcGIS tools and features o highlight important ideas and methods o assist you in becoming more self-sufficient with ArcGIS help pages o as semester progresses, they will be less cookbook and a little more open ended o Don't just push the buttons to get the 'right' answer - pause to think about what you are trying to do, what info/tools are needed, and why ArcGIS is organized in a particular way. General Approach to the Course Understand the “What.”  What phenomena are we interested in studying? – Learning and discovering.  Think about the “Why.”  Why are 'spatial analysis' and GIS tools relevant? – Critical thinking.  Master the “How.”  How do we solve the problem? – decompose a question into spatial analysis and visualization components that can be handled by the data and software. How to distinguish different geographic information?  How do we represent geographic location?  How do we represent objects in space?  Are all maps equal? (Scale or level of geographic detail)  Must geographic information be mappable? (Shortest path algorithm)  Data, Information and Knowledge - where does GIS fit in?  Data – Raw geographic facts, context free.  Information – the interpretation of data. Knowledge – interpreted information based on a particular content, experience and purpose. Why Spatial information is special?  80% of all information includes spatial component  Data, Information and Knowledge - relevant at every level.  Urban planning is inherently spatial.  Spatial relationships are as relevant as spatial location.  It takes spatial analysis to understand their relationship.  Spatial data are usually voluminous.  Presentation as a map often takes a huge amount of data.  Visualization and data consistency require use of particular map projections and spatial reference system.  Distinguish among: images of a place (streetscape), aerial photo of a place (orthophoto), and a cartographic map of the same place (Mapquest)  Distinguish among: Mapquest, NOAA hurricane map, NOAA data buoy center , EPA's Enviromapper, MIT OrthoTools, traffic reports, ..., and ArcGISWhere is knowledge of geographic location, spatial analysis/manipulation/visualization capability What is GIS?  GIS is a computer-based information system that enables capture, modeling, manipulation, retrieval, analysis and presentation of geographically referenced data. (Worboys, 1997) Other definitions of GIS  A container of maps in digital form.  A computerized tool for solving geographic problems.  A spatial decision support system.  A tool for revealing what is otherwise invisible in geographic information  A tool for automatically performing operations on geographic data. Components of GIS  Hardware,  Software,  Data,  People, (humanware)  Procedure,  Network (Internet).Evolution of GIS: A Timeline from 1970s to now • • • • • • • • • The following contents of today’s lecture is derived from Longley, Goodchild, Maguire and Rhind, Geographic Information Systems and Science, 2001, as organized by Prof. Zhong-Ren Peng for 11.520 in Fall 2003. • GISytems, GIScience, GIStudies, and GIServices •  GISystems – A computerized tool that helps solve geographic problems.•  GIScience – A scientific approach to the fundamental issues arising from geographic information. •  GIStudies – the systematic study of society’s use of geographic information, including institutional, organizational and procedural issues. •  GIServices – The business of providing GIS data and analysis tools to GIS users. • These concepts are derived from Longley, e al, (2001) • Some Examples of GIS Applications •  Resources inventory (what is available at where?) •  Network Analysis (How to get to a place in the shortest amount of time?) •  Location Analysis (Where is the best place to locate a shopping mall?) •  Terrain Analysis (What is the danger zone for a natural disaster? Visibility analysis) •  Spatio-Temporal Analysis (What has changed at what locations over the last twenty years, and why?) • • Overview of ArcGIS software • What are the various parts of ArcGIS and what do they do • How is ArcMap organized • Understanding the 'vector' and 'raster' data models underlying ArcGIS • 'Vector' data models for geospatial location • Geometry model: o boundary representation 'vector' model o points (sales), lines (streets), and polygons (block groups) o assign spatial feature ID to each spatial object • Attribute data model o relational tables linked to spatial features via IDo graphical interface to utilize geometry/attribute links • Complications o islands, lakes, overpasses o share edges?, move links when you move points? o ambiguity: summer/winter wetland boundaries o scale, generalization, conflation, slivers o Coordinate systems and projections • Thematic mapping - tip of iceberg regarding GIS applications o Symbology  many options  review 'symbology' page of layer properties  review ArcGIS help files for symbology o Different classification schemes (show help page):  Equal Interval  Natural Breaks  Quantile  Standard Deviation o Normalization: people or population density - Why do we care? (show examples) Raster vs. vector data models • regular grid on top of spatial features (instead of encoding boundary) • pixel brightness in orthophoto of Boston • Vector: points,