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



Lecture One: Overview of Course, GIS Principles, Elements of Maps, ArcGIS Basics

 

September 5, 2007

1. Overview of Course

·        Syllabus/Lectures/Labs/Homeworks/Project

·        Course Website: http://web.mit.edu/11.520/www

·        Other GIS courses: 11.913, 11.220, 11.521, IAP miniclasses, Harvard, BU,...

·        Student background

2. GIS Principles

2.1 Geographic information

  • is information about places—spatial dimension
  • 80% of all information include spatial component - how should one embed location in data
  • knowledge about both where something is and what it is - with query capability in both directions 
  • geographic resolution
    • very detailed
      • information about the locations of all buildings in a city
      • information about individual trees in a forest
    • very coarse
      • climate of a large region
      • population density of an entire country
  • characteristics
    • often relatively static-- e.g., GPS coordinates of fixed features
      • natural features and many features of human origin don't change rapidly
      • static information is easier to portray on a static paper map
    • can be very voluminous
      • a terabyte (1012 bytes) of data is sent from a single satellite in one day
      • gigabytes (gigabyte = 109 bytes) of data are needed to describe the US street network

Abstraction--Geometrical Representation

  • Model spatial objects by describing their boundaries (vector data models)
    • Use coordinates that locate the spatial objects on the Earth
    • Point--a single location is often sufficient
      • MBTA Stops
      • Is Boston a point?--At different scales or for different purposes, Boston could be a point or polygon.
    • Line--only one dimension needs to be represented
      • Street centerline, MBTA Railroad track, ridgeline, bux route
      • How does it matter if street is modeled as centerline or as the void between blocks?
    • Polygon--2D planar surfaces
      • Cambridge border, central square boundary, census tract, parcel, ...
      • What about river boundary, edge of ocean (at high tide?)
    • Beyond planar surfaces - terrain models, 3D CAD models, ...
  • Model the space that contains spatial objects (raster data models)
    • Divide space into 'cells' and encode whether a spatial object is in each cell
    • 30m x 30m grid cells for Landsat image - classified based on predominate land use within each cell
    • 6 inch pixels for color orthophotos developed from aerial photography
    • 3 km x 3km x 1 km (height) volumes for meterological modeling

2.2 Five examples to view and discuss: which are GIS? what to learn? how to add your own data/analyses?

  • Private sector mapping services
    • Mapquest or Google-Maps to find a location and generate a street map: www.mapquest.com
    • Google-Earth (and Keyhole, Digital Earth, etc.) to navigate and 'fly' over the earth: earth.google.com
  • Spatial analysis using commercial GIS software
    • ArcGIS to analyze the demographics and economic development potential of Appalachia - we'll use ArcGIS
  • Web services using open-source (LAMP) tools
    • Compare ways of accessing data on MassGIS website: http://www.mass.gov/mgis
    • via ordinary browser, Oliver (java) applet, and Web Mapping Service (WMS) protocols

2.3 Geographic information systems

2.3.1 Definition

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.
  • Methods of embedding geographic location in data in ways that facilitate spatial analysis

2.3.2 Components of GIS

  • Hardware, Software, Data, People, Procedure, Network (Internet)
  • GIS hardware is no longer extraordinary (nothing special about the hardware)
    • but often benefits from extra components
      • large monitor, disk drive, RAM
      • special (large) printers/plotters (for large, detailed, color maps)
      • special input devices (scanners, digitizers, GPS recorders, PDAs, etc.)
  • software vendors
  • what is important about the information that's stored and analyzed
    • representing and managing i nformation about what is where
      • the contents of maps and images
      • BUT what is stored may 'look' very different
    • special functions that work on geographic information, functions to:
      • display on the screen (interconnected maps and tables)
      • edit, change, transform (via map or table)
      • measure distances, areas, proximity, adjacency
      • combine (overlay) maps of the same area together

2.3.3 Example GIS Applications

  • Resources inventory (what is available where?)
  • Thematic maps (spatial pattern of population density, income, household size, etc.)
  • 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 (Land use: what has changed over the last twenty years, and why?)

2.3.4 what does it mean to be "doing GIS"?

  • using the tools of Geographic Information Systems to solve a problem
    • such as those in the previous examples
    • a GIS project might have the following stages:
      1. define the problem
      2. acquire the software (and the hardware?)
      3. acquire the data
      4. clean the database
      5. perform the analysis
      6. interpret and present the results
      7. institutionalize the process so that the analysis can be routinely redone
  • GIS tools and techniques are becoming more integrated with other tools and/or embedded in web services
    • Do spatial analysis without being 'in' a GIS package
    • Include location, spatial indexing, etc. in general purpose database management tools

3. Elements of the Map

  • Scale (Distance on the map compared with distance on the earth)
  • Symbolization
  • Projection
  • ... Ignore for today and jump into ArcMap to get a feel for key features of a typical GIS package
    • We'll pay more attention to maps, data models, and ArcGIS basics in other lectures or in lab

 

4. ArcGIS Basics-- preview of Lab Exercise 1

Mapping Cambridge home sales and household income

Things to think about

  • Setting Up a Work Environment
    • Starting an ArcGIS
    • Setting up workspace, scratch, database, etc.
  • Getting Data Into ArcMap
    • Data Frame Properties: Name, Units (Map, Display)
    • Layer Property
    • Tool in/out
    • Attribute Data
  • Basic Map Making
    • Simple Symbolization
    • Thematic Symbolization
  • Saving Your Work and Printing Output

For now

  • Explore cross-referencing of map and data tables
  • Discuss data model for geometry and attributes
  • Compare uses of ArcMap with those of Mapquest and Google Earth

For MONDAY - go directly to the lab (Room 37-312) at 2 PM

  • From Syllabus - do introductory readings (Worboys pp 1-15 and intro from NCGIA curriculum)
  • Need combination lock plus MIT card to access the lab and MIT (athena/email) ID to login.
  • ArcGIS software is also available for installation on personal computers
    • but, will only work when networked to MIT with a valid MIT ID)
    • requires other software (Kerberos and VPN to connect from off campus, AFS to access data)

 


Created by Prof. Zhong-Reng Peng, September 2nd, 2003.
Modified by Jinhua Zhao, September 7th, 2004.

Last Modified by Joseph Ferreira, September 4th, 2007.

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