Post on 29-Nov-2014
description
GIS Workshop
Concepts and Practice
Nancy Warren, MPH
With Contributions from:
Nathan Heard, DSc
Hilary Spindler, MPH
Sarah Gutin
Ryan Keating
Goal
• Understand important GIS concepts and
how to utilize them through Quantum
GIS (QGIS), an open source software
package
Objectives:
• Understand basic GIS concepts
• Navigate GIS interface
• Locate GIS data on the web and
identify reliable data sources
• Add data to GIS software and
prepare vector GIS data
• Convert text-based data to a GIS
format
Objectives (cont’d)
• Create thematic maps with multiple
variables
• “Clip” map sections
• Test maps with Google raster data
• Demonstrate competency with basic
QGIS
Session one:
• Overview
• Basic QGIS installation and navigation
• Loading shapefiles and navigating
shapefiles
Definition of GIS
• Geographical Information System
– A map connected to a database
• A computerized database management
system for analysis and display of spatial data
• A system of data and tools
Why GIS?
Isn’t this chart enough?
Province HIV prev: women Cabo delgado 9.5 Gaza 29.9 Inhambane 10 Manica 15.6 Maputo 20 Nampula 5.5 Niassa 3.3 Sofala 17.8 Tete 8 Zambezia 15.3
Why GIS? see it to understand it:
HIV prevalence in women
Functions of GIS
• Visualization and Mapping
• Spatial database management
• Spatial Analysis
What GIS Applications Do:
• Automate geographic data
– Produce maps
– Calculate areas, distances, route lengths
• Integrate data (i.e. property maps and satellite photos)
• Communicate complex spatial patterns
What GIS Applications Do
• Answer spatial queries
– (how many HIV+ people live further than 10 km
from the PMTCT clinic 24 de Julho in the
Zambezia province?)
• Perform complex spatial modeling
– (“what if” scenarios for resource management –
where to put new sites, transportation – how to get
resources to people in need, etc.)
Difficulties
• Difficulty of database creation
• Integration of data from diverse sources can
result in poor overall accuracy if not well
managed
• Representation of dynamic data – flows,
dispersion, people, time can be problematic
The GIS Data Model: Implementation Geographic Integration of Information
Layers
By
Organized
Is
Data
Data Organization in GIS
• Each layer contains
one specific type of
information.
• Layers are
integrated using
their geographic
location on the
earth’s surface as
the organizing
principle
Layers can be represented as Rasters or
Vectors:
•Vector create feature layers
– Point
– Lines (direction and length)
– Polygons (area, centroids,
and perimeter)
•Raster create surface layers
– Records information about
each element on a fixed grid
as pixels (E.g.: Satellite
images, aerial photos)
Vector vs. Raster
Table or attribute data
Tables - contain data for places that can
be converted to GIS files and mapped
• If each data record contains unique ID
codes for each place, those records can
be joined to their corresponding
features in a GIS file and mapped.
• If the data contains coordinates like
latitude and longitude, the data can be
plotted and converted to a vector file.
Geodatabase •A geodatabase
(short for geographic
database) is a
physical store of
geographic
information in the
form of features and
classes inside a
database
management system
(DBMS).
Linking data: JOIN
GIS systems maintain
• spatial and
• attribute data separately,
• then “join” them for display or analysis
JOINing our data:
Geographic data links
• Spatial data
Attribute data
Metadata: an important
part of GIS infrastructure
• Describes information resources
• Enables data exchange, efficient use of
(existing) resources
Source: http://www.esi.utexas.edu/gk12/workshops/gis/ppts.php
Quantum GIS (QGIS) - freeware
• Open Source GIS software that runs on Linux, Mac, Unix and Windows
• First released in 2002 – Mature program – Strong Online Community
• Regular updates and releases
• Compatible with: MySQL, SQLite,
• Freestanding module that can be linked
QGIS • View and explore spatial data
– Can use files from other programs: Google
maps, Open Street Maps, WMS, GRASS
• Map Data (e.g., prevalence, population)
• Create/edit spatial data (e.g., from GPS
unit)
• Perform Spatial Analysis (e.g., network
analysis)
QGIS: Disadvantages
• Learning curve is higher
• No raster or vector data already
included -- must import
• No raster or vector data integrated --
must ensure quality
• Importing table (attribute) data is a two
step process
QGIS relies on other sources
for map layers
• User needs to import mapping layers
into the system from their own sources
and
• user needs to ensure quality of layers
-DIVA GIS
-QGIS
Open Streets Maps and
Google Maps – These offer layers that can be imported
and used with all the other GIS software
we will discuss today
– Can be manipulated to show a variety of
features
Google Maps and Google
Earth
• Disadvantages:
– No static layers that can be imported and
used, because layers are constantly being
updated
– Requires strong connection to web in order
to import layers
5 minute QGIS Tour
When you first start up QGIS, this is what you will see.
This is called the QGIS Graphical User Interface, or GUI
It may look bare now, but by the end of this week, the GUI will look a little more like….
This!
Lets take a moment before going any further and go through the front-end components of QGIS.
Becoming familiar and comfortable will make learning the ins-and-outs of QGIS a little easier
We can think about QGIS in terms of a geodatabase.
We can see all of our vector and raster data in the left hand layers window
Whenever we load or create a new layer, it will appear in this window
This is where our data will be visually represented.
In this example we can see two types of spatial data. Raster and Vector.
In terms of vector data we can see two types: line and point data.
Both of these visual data elements are also visible in the Layers window
The raster data we can see here is this large satellite image of Vilankulos.
What do we need before
starting?
1. QGIS Software
2. Data (Shapefiles)
3. Plug-ins
QGIS: Required Software
• QGIS Desktop (Standalone Installer)
This tutorial was designed with version 1.7.3 WROCLAW. In an effort to improve quality control, QGIS next version (LISBOA) has made access to some of the 3rd party plugins very difficult so we recommend downloading this first and getting your plugins.
http://qgis.org/downloads
Data = Shapefiles
• Like most GIS software, QGIS
organizes its data along raster and
vector layers.
• These layers can also be referred to as
Shapefiles.
• Shapefiles can either be created by the
user or found on Online Spatial Data
Repositories
Online Spatial Data
Repositories • DIVA – Free Spatial Data (Solid source of
administrative boundaries, rails, roads &
inland water)
– http://www.diva-gis.org/gdata
• CloudMade – Downloads (Excellent open
source repository)
– http://downloads.cloudmade.com
Essential Plug-ins
• Open Streets Plug-in: Allows you to
directly download Open Streets Map data
(Vector and Raster) to QGIS
• Open Layers: Allows you to view Google,
Yahoo and OSM map in QGIS (Raster
only)
• Add Delimited Text Layer: Allow for easy
importing of a GIS-data-containing
spreadsheet
To begin we need to install
basic software:
1. QGIS
You want WROCLAW, version,
1.7.3 available here:
http://qgis.org/downloads/
2. LibreOffice http://www.libreoffice.org/download/
This program is required to add our data to existing spatial
data
How to Add Plug-ins
In order to add plug-ins first click on the “Plugins” Dropdown menu
In order to add plug-ins click “Fetch Python Plugins..”, highlight in the Installer window, and click “Install Plugin”
Optional depends on your web
access/connection
In order to add plug-ins click “Fetch Python Plugins”, highlight open streets and open layers in the Installer window, and click “Install Plugin”
The installed plugin will then be available in the same drop-down menu
Once installed, the plug-in will be available either on the dropdown menu or on the plugin Palette below
Now that our plug-ins are downloaded, we need to enable them. Click on “Manage Plugins…” in the Plugins drop-down menu
Make sure that the plugins you want to use are checked. For our purposes, check “Add Delimited Text Layer”, “Open Layers” and “Open Streets Plug-in”
Click “OK”
Exploring the Interface
• QGIS is very simple to navigate. It's
made up of a layout area where the
map is drawn surrounded by a toolbar,
layers panel and a status bar.
Len De Groot, UC Berkeley School of Journalism QGIS basics for journalists
http://multimedia.journalism.berkeley.edu/tutorials/qgis-basics-journalists/
Toolbars
• Toolbars can be controlled and turned
off or on in the Toolbars menu.
• Can arrange them by clicking and
dragging.
• Can configure the toolbars to your liking
(suggestion: aligning them so you have
only two rows of them at the top of the
screen and all buttons are visible)
QGIS has many toolbars, but they are grouped for easy identification
Now you explore!
• Plug ins
• Toolbars
• General interface
Loading Pre-existing
Shapefiles: Vectors
Download shapefiles: Diva
Choose administrative areas
Note the definitions of the layers are
down below the pull down menu
Click “ok”
Map pops up on next page:
bottom of page - hit download
Drag the files to new folder:
zambia shapefiles
Loading Pre-existing
Shapefiles: Vectors
Click add Vector Layer to add shapefile.
Once the “Add Vector Layer” dialog is open, click browse.
Highlight all .shp files & “open”
And again click “open”
You will see the directory and the file name of the shapefile you chose in the “Source” dialog box.
Now you see Zambia!
Notice that the layer appears in the map and the layer window.
As mentioned before, vector layers can either be points, lines, or areas. This is an area layer
Click through the diff layers
It is quite easy to change these boundaries with one click. Note how the previous layer 2 disappears and now we see layer one.
Note how the boundary levels change with the #s. 2 is “district” boundaries, 1 is province and 0 is…?
You can also
simply move the
layer up – the
layer at the top is
the one that
shows in the
screen
Notice that we have just added a point-type vector layer. By the end of the course you will take raw health facility data convert it into a shapefile and be able to place it in into existing map layers like this!
End session one:
THANK YOU!