1. I ♥ Maps: quantum Gis + Python
August 6th, 2014
Paige Bailey
Explanation of why GIS + Python means a lot to me, personally
Unsure of how to go about creating the slide deck
Laying out the “why?” and hoping people get inspired

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:
* Geology data in Microsoft Excel

6. …but when mapped:
* Same data, mapped in ArcGIS

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 https://www.flickr.com/groups/qgis/pool/

18. Some beautiful examples of qgis maps

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?
[handout]

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]
Make sure to mention qgis is a dot file, so not immediately visible

24. Let’s make a thing!
Make sure to print off steps!!

25. Questions?
Thanks!