Prepared as part of the IT for Business Intelligence course of MBA @VGSOM, IIT Kharagpur. The tutorial describes how to represent vector data on a map using the open source software QGIS.
1. QGIS Introductory Presentation
Prepared By:
Niloy Ghosh
Nitin Kumar Rathore
Students of 2nd Year MBA at Vinod Gupta School of Management
(VGSOM), IIT Kharagpur
2. What is QGIS?
• Quantum Geographical Information Systems (GIS)
is an Open Source Geographic Information
System software
• It is a system designed to capture, store,
manipulate, analyze, manage, and present all
types of geographically referenced data
• The QGIS desktop offers many functions for
viewing, editing, and analysis of data.
• Data can be exported to Mapfiles to be viewed as
webpages without using QGIS
3. About GIS
• GIS allows us to view, understand, question,
interpret, and visualize data in many ways that
reveal relationships, patterns, and trends in
the form of maps, globes, reports, and charts.
• It can be used to map and monitor data as
well as changes in it over a period so as to
take appropriate action
• We would be using the QGIS version 1.7.3
called Wroclaw
4. Data
• The data for the QGIS consists of 2 forms
– Raster: a regular grid made up of cells, or in the case of imagery, pixels having
a fixed number of rows and columns. Each cell has a numeric value and has a
certain geographic size.
– Vector: describing a location by using a set of coordinates. Each coordinate
refers to a geographic location using a system of x and y values.
• For our demo purpose we would be using “shapefiles” which are a digital
vector storage format for storing geometric location and associated
attribute information.
• It is a collection of files which need to be stored in the same location. The
3 mandatory one are:
– .shp — shape format
– .shx — shape index format
– .dbf — attribute format
• The other data that would be mapped can be obtained as tab-delimited
files or .csv files from various sources.
10. •Go back to the Plugin Installer and add the 3rd Party Repositories
•Under the Plugins Tab search for the required plugin and Click the Install plugin button
12. Getting the data
• Shapefile
– The shapefile can be obtained from the site
http://www.naturalearthdata.com/
– Download the ‘ne_10m_admin_0_countries’ shapefile
• Data
– The earthquake related data can be downloaded from
the website
http://www.ngdc.noaa.gov/nndc/struts/form?t=1016
50&s=1&d=1 in a tab-delimited text file format.
15. •Browse and add File Name
•See that the Selected delimiter is a ‘Tab’
•In X Y fields LONGITUDE and LATITUDE should be selected (if not change them manually)
•Click OK
27. In order to make the made more legible, Right Click on the countries
Layer and select Properties
28. •In the Style Tab, increase the Transparency to 80%
•Click OK
29. Zoom in on the region you want to analyse more closely
30. Right Click on the earthquake_filtered Layer and select Properties
31. In the Style Tab, select Graduated from the drop-down menu
32. •In the Column field select DEATHS
•Select a appropriate Color ramp
•Select Mode as Natural Breaks (Jenks)
•Select Classes as 5
•Click on Classify
•Click on Apply
33. •Click on Avanced Tab
•Select the Size scale field and Select Intensity
•Click on Apply
34. In the QGIS canvas, the two factors would be displayed
•The color denotes the number of Deaths
•The size of the circle denotes the Intensity of the earthquake
35. •To correct the overlapping circles, we can reduce their size
•Go to the Layer Properties
•Click on Change button
36. •Change the Size of the Symbols to an appropriate value
•You would need to classify and apply the data again after the change
37. You may change the Number of Classes, the Size of the symbol, or the color
scheme to enhance the maps readability
38. Export the data to a HTML file
•To save the data as a HTML file, go to Plugins Html Image Map Plugin Image Map
40. •The final HTML file will be as seen below.
•On hovering the mouse over a particular region, the number at the left hand
corner displays the no. of deaths
