QGIS for Geoscientists

Robin Armit, Tom Carmichael, Lachlan Grose

Monash Structural Geophysics group

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 GIS
• A geographic information system (GIS) is a system
designed to capture, store, manipulate, analyze,
manage, and present all types of spatial data.

• From tracking diseases to vectors to

mineralisation.

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GIS

GIS

3-4D External data

modelling analysis
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 GIS

• QGIS is a open source, GIS package that can is freely available

for Windows, Mac, Linux, BSD and Android.

• As with ArcGIS, it allows you to capture, store, manipulate,

manage, conduct analyses and visualise a wide array of
Geographical data.

QGIS – Download for Windows (2.8)

QGIS – Download for Mac OS X (2.8)

QGIS – Download for Linux (2.8)

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 GIS

• QGIS has an active support community which have answers to a

wide array of questions.

QGIS – Support for users

QGIS – Documentation
QGIS – Stackexchange Forum

QGIS – Known issues and bug tracking

A QGIS FAQ for how to ask a QGIS question and increase your chances of
getting a response!

• Practical 1
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Modern Light Table

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The interface

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 A quick note on coordinate systems

• The co-ordinate system you choose

for a map (or an individual point)
defines where it appears in your GIS
project.

• Older maps often have different

datum to what is the current norm.

• Australia has moved approximately

18 centimeters since the calculation Lake Cethana - Tasmania
of GDA 94, always keep this in mind
Point in GDA 94/WGS 84 space
and check your measurements and
coordinate system! Point in AGD 66/AGD 84 co-ordinate system

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 Setting the coordinate system in QGIS
• There are two common ways to set
the coordinate system in QGIS, either
select the CRS (Coordinate reference
system) tab.

• Or, if you’re importing grids which

have already been correctly
referenced, right click on them in the
layers bar and select set project CRS
from Layer.

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 More on coordinate systems
• You must make a choice of Datum and coordinate system for your project. Normally
depends on scale and location of project.

• Making an error here can put your 100 of metres out to half the globe.

• Below is a brief summary of the Australian map grid systems.

Spheroid Datum Projection

WGS84 WGS84 World UTM (world)
AMG66 ANS70 AGD66 UTM (local using zones)
AMG84 ANS70 AGD84 UTM (local using zones)
MGA94 GRS80 AFN / GDA94 UTM (local using zones)

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 Georeferencing an image
• To georeference an image is to define where it sits in
a particular space (or this case, a defined datum).

• This is crucial for importing Raster images into your

project and using them for interpretation and
analyses of an area.

The British library has georeferenced 1000s of maps

from its archive so that they can be viewed in Google
Maps as overlays to compare with modern maps. This
is an image first created in 1857 for the British
Hydrographic survey. http://www.theatlanticcities.com/technology/2013/01/good-deed-day-help-
georeference-british-librarys-map-collection/4516/

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 Georeferencing an image
1. Choose the Georeferencer tool from the Raster menu.
• Select Open Raster from the File menu.

• Input the correct Coordinate system (AGD 66/AMG zone 54)

• From the Settings menu, choose Transformation Settings.

• Add Control Points by making sure that Add Point is highlighted then select a point on the map where the coordinates are known. Input
the required easting and northing.

• Repeat this step at least 3 times.

• Choose the transformation type: Linear, Resampling Method: Linear. Change the Target SRS to a more modern projection (WGS 84/Zone
54S). Give the file an appropriate title and location.

• Select Start Georeferencing.

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 Georeferencing an image
• Choose the Georeferencer tool from the Raster menu.

2. Select Open Raster from the File menu.

3. Input the correct Coordinate system

(AGD 66/AMG zone 54)
• From the Settings menu, choose Transformation Settings.

• Add Control Points by making sure that Add Point is highlighted then select
a point on the map where the coordinates are known. Input the required
easting and northing.

• Repeat this step at least 3 times.

• Choose the transformation type: Linear, Resampling Method: Linear.

Change the Target SRS to a more modern projection (WGS 84/Zone 54S).
Give the file an appropriate title and location.

• Select Start Georeferencing.

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 Georeferencing an image
• Choose the Georeferencer tool from the Raster menu.
• Select Open Raster from the File menu.
• Input the correct Coordinate system (AGD 66/AMG zone 54)

4. Add Control Points by making sure that Add

Point is highlighted then select a point on the
map where the coordinates are known. Input
the required easting and northing.

5. Repeat this step at least 3 times.

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 Georeferencing an image

6. From the Settings menu, choose Transformation Settings.

7. Choose the transformation type: Linear, Resampling Method: Linear. Change the
Target SRS to a more modern projection (WGS 84/Zone 54S). Give the file an
appropriate title and location.

8. Select Start Georeferencing.

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 Basemaps
Setting the coordinate system in QGIS

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 Loading a layer (Raster or Vector)
• The majority of your GIS projects will be
defined by layers made up of either Rasters or
Vectors.

• A Raster is a spatial dataset that defines space

as an array of equal sized cells arranged into
rows and columns (e.g. Satellite imagery or
referenced geological maps)

• A Vector dataset is one that is represented as

geographic features, such as points, lines and
polygons.

• Each layer type has its own drawbacks and

advantages and are used to describe different
data.

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 Loading a layer (Raster or Vector)
• Loading an existing layer is done through the
Layer menu, either by choosing Add Raster
Layer or Add Vector Layer depending the
dataset you’re importing.

• There are a range of other options depending

on what data types you have available, but
Vector and Raster are the most common.

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 Creating a new layer (Creating Points, Polylines
and Polygons)
• To better interpret your data and to get a
more detailed understanding, the creation of a
set of different datasets is required.

• On the Ararat 50K mapsheet, there are many

different features that can be observered, in
its current state the image is a Raster but
turning sections of it into a Vector can provide
more insight.

• There are features on this map that can be

turned into points, lines or polygons.

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 Creating a new layer (Creating Points, Polylines
and Polygons)
1. From the Layer menu, select New Shapefile Layer.
• From the New Vector Layer window, choose Point.

• Choose the correct CRS.

• Give the new layer at least one Attribute.

• Save the Layer in a reasonable location.

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 Creating a new layer (Creating Points, Polylines
and Polygons)
• From the Layer menu, select New Shapefile Layer.

2. From the New Vector Layer window, choose Point.

3. Choose the correct CRS.

4. Give the new layer at least one Attribute.

5. Save the Layer in a reasonable location.

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 Adding to a layer (Point)
1. Make sure that the Digitizing toolbar is selected.

2. The correct Layer needs to be highlighted (Points)

• From the Digitizing ribbon, select the Toggle Edits cursor.

• Select the Add Feature button.

• Select a point of interest, give it the Attributes that you previously assigned.

• Click Save Edits once you’ve completed adding points.

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 Adding to a layer (Point)
• Make sure that the Digitizing toolbar is selected.

• The correct Layer needs to be highlighted (Points)

3. From the Digitizing ribbon, select the Toggle Edits

cursor.

4. Select the Add Feature button.

5. Select a point of interest, give it the Attributes that

you previously assigned.

6. Click Save Edits once you’re done.

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 Polylines

• Digitizing polylines is done in the same way that the

creation of points, except that the end result is defined
by a line, instead of a single point.

• The can be used to represent a

large amount of geological data
that is defined as linear.

• It is extremely important to use

the style tool to make sure that
you can visualise what each of
your line represents.

• This will be covered later in this

course.

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 Polygons

• Layers that are created as Polygons are initially added

in the same way that polylines and points are.

• Polygons are used to define enclosed 2D areas. It is

defined by a set of (x,y) co-ordinate pairs.

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 Polygons

• Create an initial polygon by selecting four

points on the map, the program will join
these four points with straight lines.

• By using the Snapping Options from the

Settings menu and choosing the tolerance
as around 20 pixels, you can snap to a
node from your polygon when you are
close to it.

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 Polygons

• By adding extra nodes to a line, by

double clicking on the edge of a polygon
with the Node Tool selected.

• With the Node tool still selected, each of

these individual nodes can be
manoeuvred to better represent the
underlying geology.

• By doing this over the entire area you

can create a polygon that is
representative of this geology

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 Importing Tables
• The data you initially collect in the field will unlikely be in a format that you can
directly import into a GIS package.

• The easiest way to solve this is to convert a table (usually a .csv file) into something
more workable.

Using GIS it is possible to turn field data, into manipulable, useful, information

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 Importing a table

2. Select your text delimited file and fill in the data

required.

1. Choose Delimited Text Layer from the

Layer menu.

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 A quick word on tables
• It is vital that before you go out into the field, that you know what data you’re going
to collect and how your input table should be set up.

• What information do you need to record at each location?

• Do you have a comments section to record pertinent information?
• What coordinate system is my GPS in?
• Was my data input into my table correctly? (Have I qaqc’d my data?)
• Are all my measurements in Strike and dip or dip and dip direction?
• Do my numbers make sense?
• Did I record them all in the same way?

• All of these questions (and more!) need to be dealt with before you try to import
your data.

• Otherwise, any errors that you bring in will be involved in your interpretation.

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 Todays task

• Familiarisation with GIS

– Download and install QGIS

– Setup the plugins

– Import existing data

• stylise the data

– Draw onto your map

– Export as a PDF or Image file

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 Setting up the files
• http://users.monash.edu.au/~rjarmit/GIS/GFG/

• Download KANMANTOO PRAC.ZIP

• Create the following directories

• GFG
– Day1

– images

– shapefiles

• Unzip the files inside the kanmantoo into the images folder

• The otherfiles into the "shapefiles" folder

• Move all the map_extent files from images to shapefiles

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 Plugins
• Way to add extra features to the program
– QGIS plugin repository has about 500 plugins
– https://plugins.qgis.org/plugins/
– Or you could write your own
• For this course we need:
– Openlayers
– Autotrace
– Clipper
– Contour
– Generalizer
– Qgis2threejs

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The plugin manager

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Adding existing data

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 Organising your project
• Select all the images and right click group
• Select all shape files "map extent, geology of
Kannmantoo, Cambrian geology of Kanmantoo"
and group
• You can name these groups as you want

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 Stylising your shapefiles
• Find out the properties each
shapefile has:
– Right click and open attribute table
– Work out the best one to colour them
by... eg lith group
• Right click shapefile and open
properties then click the style tab
– Column == the attribute to colour them
by
– Select categorised
– Press classify

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Creating a shapefile

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 Naming and saving your files
• Use a descriptive name not "shapefile"
• Try to avoid spaces
• Try to save them in the one place
• You can save multiple lines (form lines, faults etc)
in the one shapefile no need for a shape file for
each fault type!

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 Now setup the attributes
• Think about how you will classify a line e.g. type, age etc.
• Open up the attribute table and click the pen to make the
shapefile editable.

Add new column - select the

appropriate type e.g.
integer, double or text pay
attention to the length and
precision you need

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 Adding a feature

• Add a normal fault

– Add feature draw a line (doesn't need to be a fault)
– Add the relevent attributes
• SAVE

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 Stylising the fault line
• Open the shapefile properties and classify by your
relevant column
• Double click the symbol for your "normal fault"
• Add another line
– Change to a marker line
– Change marker to an esri font that looks like a normal fault
symbol
– Change offset so marker sits on the line

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Try and make a sinistral and dextral symbol

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 You should be able to
• Import raster and vector files
• Stylise your vector files
• Create your own shapefile and assign attributes to
draw structures
• Create a polygon shapefile for lithologies
• Now we will export a map

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 Additional toolbars
Advanced editing and digitising - clipping, merging, tracing

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Advanced editing and digitising - clipping,
merging, tracing

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 Using the clipping tool
Shape to keep

• Make two polygons

share a border
• Select the polygon(s)
you want to keep
• Vector  clipper

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 Autotrace
• Alternative to using the clipping tool
• The AutoTrace plugin for QGIS allows for new polygons to be digitized based on the
vertices of pre-existing features.

• To use the AutoTrace feature, the snapping options will need to be set that it is
simple to clip a vertex.

• To use the AutoTrace tool, first Toggle Editing of a layer, then select the AutoTrace
tool.
• When snapped to a new vertex, trace along features with the shift key
• Trace the longest distance around a polygon (between two vertices) with the
ctrl+shift keys together.
AutoTrace
(Editing enabled)

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Freehand drawing

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 Generaliser
• Select your shapefile that has the lines
• Open up generaliser

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 Print composer

• The print composer is a powerful way of

exporting your map with grids, axis, labels etc.

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Once it is open add your map

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 To change the settings of the map layout

• You can resize by dragging the corners

• View -- panels : make sure item properties is
checked

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To add grid lines
• Item properties grid and add a new grid.

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To add labels

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 Adding an overview
• Add another map that is your "zoomed in" area
• Go to the main qgis window and select the area you want to
zoom in on
• Go to your new map and set map canvas extent

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 Adding an overview box on the larger map
• Now select the original map

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Changing the style of the overview outline

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 What's missing?
• Try adding a north arrow
• Scale bar
• Legend
• Export to a pdf/png/svg

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Custom forms
Select type you have used before Can increment with arrows

Choose lithos from your lithology shapefile

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Custom form for adding feature

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 Custom form for adding feature
• Create a category as a
tab – “main”
• Select main and transfer
the attributes you want
across using the >
button

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 Changing the input of attributes
• Unique values – editable gives you a drop down menu
and you can add new fields.. Prevents typos
• Range for numerical data e.g. strike 0-360 dip 0-90
• Value relation to get attributes from another shapefile

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 Using data attributes
• One of the most powerful aspects of a GIS package is the ability to highlight aspects
of a data set (be it a pointset, polygon or polyline) based on its attributes.

• Using data attributes can be used to represent properties about a data point too,
such as rotation of a symbol to represent strike and dip.

• It is also possible to save data that has certain attributes as a new dataset by using a
query to interrogate the data.

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Assigning values to data based on a
characteristic.

Select Style from the sidebar and Categorized

from the drop down menu.

Select properties from the

drop down menu of a
layer (alternatively,
double click)

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Assigning values to data based on a
characteristic.
Choose a column to categorize by, then hit classify.

By changing the symbol and colour ramp, you can create a map which is relevant to
your data.

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Strike and Dip – Example of directional
markers

• By choosing a rotation field in the Style

menu of the Layer Properties menu, it
is possible to rotate a symbol by a
certain column.

• If you have dip direction as a column,

you can rotate a symbol by this value.

• You can also scale the size of an

observation by a column too.

• In QGIS you can create your own

symbols, or download them.

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 Query Builder

• Open the General tab from the Layer Properties menu.

• Select Query Builder.

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 Query Builder
• There are several important features of the
query builder which can make your life infinitely
easier.

• If you select an option from the Fields sub-menu

and then hit sample (or all) you get the values
that are present in that field.

• By using the Operators we can build a query

which will highlight certain things.

• If we’re working with text then its easiest to choose a value from the Values because
it needs to be exact.

• The IF and AND functions can help highlight areas which have more then one
characteristic that we’re interested in.

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Query Builder

• By creating this query we can

highlight only the features
which are Silurian(Ludlow) and
are Intrusives.

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 Query Builder

• By using Save As after right clicking on the layer that you’ve built a query of will
allow you to save a Shape File which only has the characteristics that you’ve saved.

• There are more complicated Querys you can build, with more detailed explanations
of each of the query functions in the QGIS wiki.

https://www.qgis.org/en/docs/user_manual/working_with_vector/query_builder.html

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