RGS-IBG Online CPD course in GIS
Exploring Google Earth
Session 4
Google Earth is a popular geobrowser that provides an exploratory interface to a rich
series of spatial data sets. Some of these may be considered 'formal' - as they are
collected centrally and distributed in a top-down manner. Examples include the high
resolution air photography and the terrain, road and government layers. Others are
less formally produced in a 'bottom up' manner as individuals across the World
contribute information to what may be considered the 'Geographic Web' through sites
such as Wikipedia and Panaramio. Both the kinds of data and content of individual
data sets provided through Google Earth changes with some frequency.
What is a geobrowser? The best analogy to make would be that of Internet Explorer
but for geographic information. Like the internet it allows the combination of many
types of geographic data from many different sources. The biggest difference between
the World Wide Web and the geographic web however is that everything within the
latter is spatially referenced.
Is a geobrowser a GIS? This has caused and is still causing some debate. We will not
enter this however as you will see from using Google Earth it has some very similar
functionality.
Objectives
In this short practical session you will become familiar
with Google Earth. The objectives of this session are to
understand the software’s interface and briefly explore
some data.
Objectives
• Learn how to open Google Earth
• Understand Google Earth’s interface
• Become familiar with exploring data in Google Earth
• Learn how to add your own data
Exercise
1.
Open Google Earth. If it is not on the desktop then it should be
under the start menu.
You should see a screen something similar to the picture below
once it has opened.
Notice the similarity to other GIS
software. There is a map view
where the globe is. On the left is
a table of contents where layers
can be turned on and off. At the
top there are some function
buttons which you will explore
later. And finally at the top right
of the screen there are the
zooming and map navigation
tools.
Zooming and Navigation
2.
Zooming and map navigation is performed using the controls at the top right of the screen. The
following diagram shows the controls and explains their functions.
1. Click the north-up button to reset the view so that north is at the top of the screen. Click and
drag the ring to rotate your view.
2. Use the Look joystick to look around from a single vantage point, as if you were turning your
head. Click an arrow to look in that direction or continue to press down on the mouse button to
change your view. After clicking an arrow, move the mouse around on the joystick to change the
direction of motion.
3. Use the Move joystick to move your position from one place to another. Click an arrow to look in
that direction or continue to press down on the mouse button to change your view. After clicking
an arrow, move the mouse around on the joystick to change the direction of motion.
4. Use the zoom slider to zoom in or out (+ to zoom in, - to zoom out) or click the icons at the end
of the slider. As you move closer to the ground, Google Earth swoops (tilts) to change your
viewing angle to be parallel to the Earth's surface. You can turn off this automatic tilt (Tools >
Options > Navigation > Navigation controls; Mac: Google Earth > Preferences > Navigation >
Navigation controls).
Source: Google
These controls can also be performed using the mouse. Hold the right button down and pull backwards
and forwards and you can zoom in and out, or double click the left button to zoom in incrementally and
double click the right mouse button to zoom out incrementally. Pressing the left button enables you to
pan the map. Get a feel for these controls.
3.
4.
Next, find a particular location using Google Earth’s search
feature. At the top left of the screen you will see ‘Fly to’. In the
box below type ‘London, UK’. The map should zoom into England,
and then to London.
Now type ‘SW7 2AR’ into the ‘Fly to’ box. You may recognise the
buildings, most obvious is the Royal Albert Hall, to the east of this
(to the west of the red bus) is the Royal Geographical Society.
Using the navigation controls explore the area.
Google Earth streams the data it needs, the data itself is not on
your computer, therefore be patient if at first it appears at a poor
resolution. You can also get a feel for the data behind Google
Earth. You can see aerial images and you have searched Google
Earth using place names as well as postcodes.
Some Simple Functions
5. Google Earth has some simple functionality. Experiment with
the Measurement tool (the button with the picture of the
ruler). Tip: Use the ‘Line’ tab to measure a single distance
(press left mouse button once to start and then again to
finish), use the ‘Path’ tab to measure cumulative distances
(press left mouse button once to start and then again at
each change of direction and double click to finish). If you
make a mistake or wish to take another measurement press
‘Clear’.
6. Experiment with the buttons with a sun behind a cloud and
a clock on them. Once you have pressed the former use the
slider to investigate what time the sun sets and rises. The
button with the clock on it allows you to look at old Google
Earth data. Again, this is controlled with the use of a slider.
Google Earth in 3D
7.
Again, using the ‘Fly to’ function type in ‘Snowdon’. Once the data
has loaded you may need to zoom out a little to see Snowdon
properly. Now explore the 3D functionality of Google Earth. Using
the scroll wheel in the middle of your mouse press it down and
roll it backwards. Make sure the ‘Terrain’ layer is switch on. You
now see Snowdon in 3D. Again explore the navigation controls
allowing you to zoom in and out and ‘fly’ around Snowdon in this
3D view.
The Geographic Web
8.
You will have noticed different markers and symbols dotted
around, especially if the Geographic Web layer is turned on. Press
on some of these. These are the ‘less formal, bottom-up’ types of
data comprising the Geographic Web which have been uploaded
by individuals. Some are photos, others are descriptions of places
of interest and so on. You will learn to create these at a later.
Adding Data
9. As well as viewing published information it is also
possible to load your own data into Google Earth.
Having watched the video you will now look at John
Snow’s map.
In Google Earth go to File > Open. Navigate to your
personal folder and select ‘snow’. This is John Snow’s
famous cholera map. This file has been georeferenced
meaning it will overlay Google Earth in the correct
position.
10. Finally, using the horizontal bar under ‘Places’ on the
left of the screen, move the slider to the left. This
allows you to alter the map’s transparency.
Summary
You should now know;
• How to find places and navigate within Google Earth
• How to measure distances in Google Earth
• That Google Earth not only has a large amount of integrated
data behind it but that it also allows people to add their own
Further Exercise
Think about all the types of data that is used within Google Earth. What sort of
spatial problems can Google Earth help us understand. Remember, Google
Earth does not have the functionality of other GIS software.