Quantum GIS (QGIS) is an open-source, highly customizable geospatial application that's great for data exploration, manipulation, and cartographic preparation -- in other words, it's software that allows you to make detailed, aesthetically-pleasing maps for free! QGIS is also *extremely* script-able with Python, and integrates with a large number of database and analysis backends (GRASS, R, PostGIS, etc.). In this talk, Paige Bailey will be giving a short overview of QGIS; detailing a few mapping case studies; then showing how to leverage additional functionality by writing custom Python plugins.

2. THREE W’S OF GEOGRAPHY:
What is where?
Why is it there?
…and why do I care?

3. WHAT IS A GIS?
GIS = stands for “geographic information system”, “geographical information
science”, or “geospatial information studies”, depending on who you talk to
GIS is an ecoystem of computer software; hardware and data; and personnel to
help manipulate, analyze and present information that is tied to a spatial
location.
• Spatial location – usually a geographic location
• Information – visualization of analysis of data
• System – linking software, hardware, data
• People – a user and analyst of all of the above!
What you’re really after are “Smart Maps” – visualizing, manipulating, analyzing,
and displaying spatial data, connected to a database.

4. …AND WHAT IS A GIS NOT?
• GPS – global positioning system (though these do come into play to
obtain geographic coordiantes quite often)
• A static, unchanging map – paper or digital
• Maps are often the product of a GIS, but are just a way to visualize the
analysis
• The magic comes by separating the variables and making it dynamic
• A specific software package, like QGIS or ArcGIS
• Estimates are that 80% of all data has some sort of spatial component

5. DATABASES AREN’T REALLY ALL THAT EASY TO
INTERPRET, CONNECTIONS AREN’T EASY TO SEE:

6. …BUT WHEN MAPPED:

7. INPUTTING AND VISUALIZING DATA
• Raster – like a grid
• Pixels
• Each pixel has a location and value
• Satelite images and aerial photos are examples
• Vector – linear
• Comprised of points, lines, and polygons
• “Features” (house, lake, etc.)
• Features have “attributes”: size, type, length, etc.

8. WHAT IS QUANTUM GIS?
• Quantum GIS (QGIS) is an open-source desktop GIS
product that helps you visualize, manage, edit, analyze, and
compose maps with geographic data.
• Runs on Linux, Unix, Mac OSX, and Windows
• Supports vector, raster, and database formats – and these
formats can be obtained from anywhere
• GNU Public License
• Written in C++
• Uses the Qt library
• Allows integration of plugins developed using either C++ or
Python

9. HISTORY AND COMMUNITY
• Was started in May 2002
• Has a huge user community, and is constantly growing – web site,
source code (SVN), bug tracker, and mailing lists are hosted and
partially maintained by OSGeo.org
• Project Steering Committee – international team of developers and GIS
users who each have a specific area of responsibility (development,
release management, community resources, finance & marketing)
• Ways for you to contribute (if you want): code contributions, bug fixes,
bug reports, contributed documentation, advocacy, supporting other
users on mailing lists and the QGIS Forum

10. SOME WAYS THAT GIS IS USED:
• Emergency services: -- rescue groups, firefighters, police
• Environmental -- monitoring and modeling
• Business – site locations, delivery systems, customer locations,
“geotriggers”
• Industry – transportation, communication, mining, pipelines, oil, health
care
• Government – local, state, federal, military
• Education – research, as a teaching tool, administration

11. SPECIFIC CASE STUDIES
Networking solutions – route optimization, like Google Maps
Ecosystem Management – tracking deforestation, migration of species,
endangered species, protected animals and plants
Oil and mineral exploration – three-dimensional visualization with leases,
wells
Environmental monitoring of a toxic plume or oil spill
Modeling of social demographics, -- how populations change over time
Facilities mapping – can show where specific areas are in an office
building, where trees are on Rice’s campus, where patients are in a
hospital

12. ROUTE OPTIMIZATION

13. SPECIES PATTERNS

14. MAPPING OIL CONTAMINATION

15. SOCIAL DEMOGRAPHICS

16. RICE UNIVERSITY TREE MAP

17. GEOLOGICAL MODELING

18. SOME BEAUTIFUL EXAMPLES OF QGIS MAPS
https://www.flickr.com/groups/qgis/pool/
https://www.flickr.com/groups/qgis-screenshots/

19. WHY IS PYTHON A GOOD FIT FOR QGIS?
• Clear, readable syntax
• Implemented in many languages (C/C++, but also Java’s Jython and
.NET’s IronPython)
• Can be used to access tons of OSGeo libraries and software
• QGIS
• PostGIS
• GDAL/OGR
• GEOS
• JTS
• GeoTools
• Proj4
• Mapserver
• gvSIG

20. WHAT IS QT ? AND PYQYT?
• Qt helps you build graphical user interfaces
• Developed by Nokia
• Exists in Google Earth, Virtual Box, Skype, Autodesk, Android smart
phones, QGIS
• Qt is built using the C++ language – supports a number of compilers
• PyQt = Python bindings that wrap C++ Qt libraries,. This is great,
because it means that we can build Qt applications without learning
C++

21. QGIS + PYTHON
• Plugins – can create your own, or install public or private. Allows users
to create / extend editing tools that interact with data inside the QGIS
environment
• Python console – command line terminal inside QGIS that allows you to
test out ideas and make quick one-off jobs. Can interact with layers
that are loaded into QGIS, access their attributes and geometry
• Python scripts and applications – writing applications from scratch that
are built off QGIS and Qt libraries (we’re not doing that today)

22. PLAYING WITH THE PYTHON CONSOLE
• Accessing layers
• activeLayer()
• QgsMapCanvas
• Visible layers vs. layers in the order they’re stacked in the table of contents
• Loading layers into QGIS
• addVectorLayer() – takes three args (path, basename, provider key)
• addRasterLayer() – takes two args (path and basename)
• Accessing vector geometry
• OgsGeometry
• Buffer, intersection, combine, difference
• Accessing data attributes
• What’s the name of the selected feature?
• What values does this raster cell have?
• How many features meet this filtering requirement?

23. INSTALLING QGIS PLUGINS
[ open up QGIS, show where the plugins are housed]
[install a random public one]
[show how you can investigate the .py files using a terminal window in
/.qgis2/python/plugins]
[encourage folks to change parameters and recompile to see how layers
change, once they check out Python QGIS Cookbook]