Introduction to GIS using Open Source Software

NOTE: This is an old version of this manual, written for QGIS 1.7. For the latest version (written for QGIS 1.8) go here.

This tutorial was created to accompany the GIS Practicum, a day-long workshop offered by the Newman Library at Baruch College CUNY that introduces participants to geographic information systems (GIS) using the open source software QGIS. The practicum introduces GIS as a concept for envisioning information and as a tool for conducting geographic analyses and creating maps. Participants learn how to navigate a GIS interface, how to prepare layers and conduct a basic geographic analysis, and how to create thematic maps.

This tutorial was written using QGIS version 1.7 "Wroclaw", a cross-platform (Windows, Mac, Linux) desktop GIS software package. Salient changes from previous versions (1.5 and 1.6) are noted in the text. You can download the software and user manual from the QGIS website at http://www.qgis.org/. The data used for the tutorial can be downloaded here or from the GIS Practicum page under the Tutorials and Courses tab on the Baruch GIS subject guide at http://guides.newman.baruch.cuny.edu/gis. Once you download and unzip the file, you'll see that the data files are separated into different folders for each part of the tutorial.

This tutorial and associated screenshots were created using QGIS in a Windows operating system. The names of certain tools and menus may vary slightly between operating systems, but functionality should be the same.

This document is divided into five parts and several subsections. Each subsection begins with steps for learning a specific application or process (the what and when), followed by commentary that explains various facets of the process (the how and why). The process and the commentary were separated in order to keep the steps as concise and easy to follow as possible with few digressions; you follow the steps first, and then go back and understand the details of why you followed the steps you did.

Objectives

Participants will be able to bring both the tools and the knowledge they gain from this workshop to enhance their projects and the organizations they work for. Specifically, this workshop will enable participants to:

• Add data to GIS software and navigate a GIS interface
• Perform basic geoprocessing operations for preparing vector GIS data
• Convert text-based data to a GIS data format
• Conduct geographic analyses using standard GIS tools and vector data
• Create thematic maps using the principles of map projections, data classification, symbolization, and cartographic design
• Locate GIS data on the web and consider the merits of different data sources
• Demonstrate competency with a specific GIS package (open source QGIS)
• Identify other GIS topics (tools and techniques for analysis), data formats (raster, vector), and software (open source and ArcGIS) to pursue for future study

Outline

• Part 1: General introduction and overview of GIS
• Part 2: Introduction to GIS Interface (learn how to navigate the interface: adding data, layering data, symbolization, changing zoom, viewing attributes, viewing attribute table, making basic selections, difference between data formats, organizing projects and data)
• Part 3: GIS Analysis (using site selection example in NYC, basic geoprocessing tasks, attribute table joins, plotting coordinate data, buffers, basic statistics, advanced selection)
• Part 4: Thematic mapping (using US states as an example, map projections, coordinate systems, data classification, symbolization, calculated fields, labeling, map layouts)
• Part 5: Going Further with GIS (exploring and evaluating online sources for free data, exploring open source and ArcGIS software resources for learning more)

Table of Contents

1. An Overview of GIS
   1. Basic GIS Concepts
   2. GIS Software
   3. Open Source
2. Exploring the Interface
   1. The QGIS Interface
      • Steps
      • Interface
   2. Adding Vector Data
      • Steps
      • Shapefiles
      • Adding Data to a Map View
      • Drawing Order
   3. Exploring the Map View
      • Steps
      • Measuring Distances and Areas
   4. Exploring Features
      • Steps
      • Attribute Tables
   5. Adding Raster Data
      • Steps
      • Raster Data
   6. Saving Your Project
      • Steps
      • Project Files
3. Geographic Analysis
   1. Creating New Project from Existing One
      • Steps
      • Saving Projects and Removing Layers
   2. Geoprocessing Shapefiles
      • Steps
      • Geographic Units
      • TIGER Line Files
      • Geographic Selection
      • Geoprocessing
      • File Naming Conventions
   3. Joining and Mapping Attribute Data
      • Steps
      • Census Data
      • Identifiers
      • DBF Files
   4. Plotting Coordinate Data
      • Steps
      • Coordinate Data Sources
      • Delimited Text Files
   5. Running Statistics and Querying Attributes
      • Steps
      • Selection Criteria
      • Some Basic SQL
   6. Drawing Buffers and Making Selections
      • Steps
      • Buffers and Distance Measurement
      • File Management
      • Site Selection
   7. Screen Captures
      • Steps
      • Considerations and Next Steps
4. Thematic Mapping
   1. Transforming Map Projections
      • Steps
      • Understanding Coordinate Reference Systems
      • Latitude and Longitude
      • Map Projections
      • GCS Definitions
      • Defining Undefined Projections
      • QGIS Projection Handling
   2. More Geoprocessing
      • Steps
      • Singlepart and Multipart Features
      • Generalization and Scale
      • CSV Files
   3. Creating Calculated Fields
      • Steps
      • Representing Values
      • Location Quotients
      • Industrial Classification: NAICS
   4. Classifying and Symbolizing Data
      • Steps
      • Data Classification and Color Schemes
      • Colorbrewer
   5. Designing Maps
      • Steps
      • QGIS Map Composer: Some Details
      • General Map Design
      • Output Formats
   6. Adding Labels
      • Steps
      • Labeling in QGIS
      • Thematic Maps and Symbols
      • Considerations and Next Steps
5. Going Further
   1. Finding Data
   2. Data Sources
   3. Additional Concepts and Applications
6. Appendix
   1. ID Codes
   2. Latitude and Longitude Distances
   3. Common CRS Definitions

Changes From Previous Manual

This manual (Version 2.0) has generally been updated from the previous version (Version 1.0) to reflect changes in QGIS software between versions 1.5 (Tethys) / 1.6 (Copiapo) and the latest version 1.7 (Wroclaw).

• Part 1 - No major changes
• Part 2 - Incorporated section on measuring distances (Section III)
• Part 3 - Updated the census data to 2007-2009 ACS, added commentary on census geography vintage 2000 vs 2010 (Section II), incorporated new table joining procedures (Section III) and new delimited text menu (Section IV)
• Part 4 - Updated the BLS data to 2009 and changed the example from Information Sector (NAICS 51) to Public Health Sector (NAICS 62), dropped projection defining step and relegated it to commentary (Section I), detailed new projection transformation procedures and added new commentary on QGIS projection handling (Section I), corrected some errors in the map projection commentary (Section I), updated table joining procedures, used CSV file for data table instead of DBF and added commentary on CSVs (Section II), added information about new feature count option (Section II), dropped location quotient from example and relegated to commentary (Section III), dropped steps on old symbology and updated with new symbology, relegated Colorbrewer to commentary (Section IV), added information on legend bug (Section IV) while dropping information about fixed PDF bug (Section V), rewrote labels section based on new labeling features (Section VI)
• Part 5 - Updated some broken links (Section II)
• Appendix - Added an appendix; previous version had none