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GIS course, School of Geosciences, Monash University.
Getting started with arcGIS
Here are a few types of maps generated with arcGIS. However there are a many different
uses for GIS and sources of GIS data.
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GIS course, School of Geosciences, Monash University.
arcGIS interface
1.
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Layers window, adding layers toggle etc.
Use the 4M scale to show broad scale stratigraphy.
Zoom in to Moyston Fault, Stawell area.
USE zoom tool, extents, pan etc. to show Ballarat 100k detail.
Zoom out to show resolution issue. Highlight the importance of scale on choosing data to
display.
Use measure tool to show distance.
Use effects toolbar for transparency and swiping.
Use identify tool to observe the units.
Bring up geophysical image and explain mapping techniques for interpet.
Image editing (properties) to highlight geophysical images eg. 1vd on tmi.
File directory importance e.g. external hard drives etc.
TO DO
Open a new .mxd and add shapefiles including:
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1:4M geology
1:100k Ballarat geology
Cities
Roads
Geophysical images grav and mag tmi and 1vd.
Vic boundaries
Mines sites
SAVE work
REVIEW work
1.
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View attributes (vic boundaries) in order to decide how to format the shapefile.
Importance of saving shapefiles as a layer file. What the difference?
Attributes can be sorted by zone name, and colour ramp, manual colour change etc.
Label zones.
Then using 100k sheet, sort by age and label with unit name to visualize multiple attributes.
TO DO
Experiment with attributes
2. Basic interpret.
TO DO
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GIS course, School of Geosciences, Monash University.
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Open ArcCatalog and produce new shapefiles e.g polylines, polygons etc.
Creating new shapefiles (point, polylines, polygons)
1. Open ArcCatalog. The button
(circled) should be found once
ArcGIS has been opened.
2. Once in ArcCatalog, browse to
the directory you wish the shapefile
to be located in. Right-click in the
right-hand pane and go to ‘New’ –
‘Shapefile’ (see left). Left-click on
‘Shapefile’
3. Enter the name of the shapefile
without using spaces. Use an
underscore if you need to separate
words (eg.
‘Andrew_Button_Prospects’)
Choose the type of shapefile you
need by left-clicking the down
arrow at the right of the ‘Feature
Type’ menu box.
Click ‘Edit’ to select the coordinate
system you are using.
Click OK to create the shapefile
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GIS course, School of Geosciences, Monash University.
4. If you need to add certain data to
your shapefile, you can create fields
to help you organise it. Right-click
the shapefile and select ‘Properties’.
Go to step 6 if this is not necessary.
5. Click on the ‘Fields’ tab at the top
of the Shapefile Properties window.
Some fields will already be added
which GIS uses to organise itself, so
it’s best to leave these alone. To add
your own field, click within the next
empty field (in this example the
fourth line down) and type in the
field name. Note that a cursor will
not appear to indicate the field is
‘active’, so just start typing. Select
the type of data you’ll be entering –
usually this is text whether it is
alpha or numeric. You can set the
field length in the area under the list
of fields, note that the values is the
number of characters (including
spaces) – not words. The default
value of 50 is normally sufficient.
Data can be added to these new
fields in editing mode within Arc
GIS.
6. To add the shapefile to your GIS
map, either click and drag from
ArcCatalog and drop into the
required location in the Table of
Contents within ArcGIS, or click on
the ‘Add Layers’ button and browse
to the files location (left)
7. Editing
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Use symbology to give the shapefiles a format and save as a layer file.
Draw a series of interpreted boundaries, regions, faults etc. using the geophysical data and
compare it to the map sheets provided.
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GIS course, School of Geosciences, Monash University.
3. Georeferencing
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Different projection systems e.g. lat, long versus geographic. Which one and why?
TO DO
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Georeference the 50k Ararat map map using AGD66 or AMG66 z54.
1. Open ArcCatalog and browse to the
image you want to georeference. Before
doing anything you need to set the
projection of the image file. Right-click
the image file and select properties. Find
the ‘spatial reference’ entry and click
‘edit’ (left). Assign the coordinate system
the image was created with (or, if
unknown, that you are using in the GIS
map) and click ‘ok’. Exit the image
properties window by clicking ‘ok’.
2. Add the image file to the ArcGIS map
with the ‘add data’ button. When the
image appears in the Table of Contents,
right-click and click ‘Zoom to layer’ to
find it.
Find the Georeferecing menu and open
the ‘Link Table’ (top-left). This will
display the entries you make as you go
(bottom-left). Un-check the ‘Auto Adjust’
box if you don’t want the image to be
moved as you add points. I prefer to keep
it on as it helps to identify if the image is
being georefenced correctly.
3. Once you have selected points on the
image that have known co-ordinates you
can start adding georeferencing points by
right-clicking and choosing ‘Enter X and
Y’. A Enter Coordinates box will appear
and you can enter the coordinates
manually. Make sure that you use either
decimal degrees (left) or Easting –
Northings format. Degrees-mins-secs
won’t work!
Three points is the minimum you need,
though I find four tends to make a better
job of it.
Note that you can save your work as you
go by clicking the ‘Save’ button. This can
save time on especially tricky images
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GIS course, School of Geosciences, Monash University.
when you may have to start again. Just
click ‘Load’ to restore the points if you
need to re-add an image from scratch.
4. When the image has been
georeferenced correctly, choose the
‘Update georeferencing’ option fro the
georeferencing menu (top-left). This will
ensure all you points have been updated.
Then click ‘Rectify’ from the same menu
to save the image and the georefencing
you have done. This will prompt you to
save the image. This is very important
to remember! If you don’t rectify and
you close the map down, you will loose
all your hard work.
When you save the image, you’ll need to
add the rectified image to the GIS map.
Remove the original image that you
added in step 2 and the georeferencing
points will be removed as well.
Note some handy options are available
from the georefencing menu. ‘Delete
Control Points’ removes the points from
the Link Table, though this can be done
by selecting a point in the Link Table
itself and clicking the ‘X’ (circled,
bottom-left). ‘Reset transformation’
allows you to start the process again if
things go awry.
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Digitise a part of the map using new shapefiles. Importance of workflow?
Draw a series of polygons and clip one from the other to highlight efficiency of clipping.
Use snapping and finish part tools to speed up drawing process.
4. Selecting attributes (structural point data file).
TO DO
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Add this point data and edit format to display different symbols e.g. s0 s1.
Symbol editing and symbol rotation.
Display only 1 fabric generation (create query etc).
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GIS course, School of Geosciences, Monash University.
Selecting specific attributes from shapefiles
1. Open the attribute table of the
shapefile you wish to use (rightclick the layer and select ‘Open
attribute table’). Once the table has
opened, click ‘Options’ at the
bottom of the window and select
‘Select By Attributes…’ (at left)
2. Select the method you wish to use
to select your attributes. ‘Create a
new selection’ is used in most
instances. Double-click the column
name you wish to sort with (in the
case to the left ‘Descrip’ is where
the age of the rock unit depicted by
the polygon is stored). Click the
operator required (eg. ‘=’) and then
enter the search keyword (eg.
‘HOLOCENE’ – at left). Please note
that words require single quotation
marks (‘HOLOCENE’) whereas
numbers do not. If you do not use
quote marks around words the
search will fail, as will using quote
marks around numbers.
3. If you get stuck click ‘Help’. This
window contains some helpful hints
and reminders that assist in entering
the correct search syntax.
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GIS course, School of Geosciences, Monash University.
4. To verify the search ‘expression’
has been entered correctly, click
‘Verify’. This will perform the
search to verify that it will return a
result, but won’t select the searched
attributes. If the search has been
entered correctly AND obtains a
result you will receive the message
to the top-left – this is good! You
can then make your selection by
clicking ‘Apply’.
If the expression was entered
correctly, but no results are returned
the message at middle-left will
appear. You may need to check
upper versus lower case or spelling.
Sometimes words can be mis-spelt
or spelt differently.
If everything was entered
incorrectly then you receive the
message at bottom-left. This means
you have entered the expression
incorrectly – it’s probably best to
use the help option from step 3 to
check what is wrong with it.
5. If all goes well with the search,
the selected objects will be
highlighted in the attribute table
(left). If you wish you can close the
Select by attribute window by
clicking close. To view only the
selected objects click ‘Selected’ at
the bottom of the window (circled)
6. To create a new layer using only
the selected attributes, right-click
the layer in the Table of Contents
and go to ‘Selection’ and click
‘Create layer from selected
features’.
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GIS course, School of Geosciences, Monash University.
7. A new layer will appear with the
same name as that of the original
layer, but with ‘selection’ added. It’s
good to rename these layers to avoid
confusion.
8. The result using the Holocene
unit example can be seen at left. The
right-hand image shows the new
layer based on selecting only
Holocene objects
5. Layout view allows the addition grids, legend, north arrow, scale etc for publication in
different formats.
Create a map (using either the dataset provided or from your field area) with
description for grading. Lucid brevity to be rewarded.
50% participation, 50% output.
GOOD LUCK with GIS.