Google Earth Tutorial: Paths
Geobrowser
The following are
notes on my GTI presentations about how to create Paths in Google Earth. If you
have questions please add a reply to this post and I respond as soon as I can
(if someone else doesn’t answer first!) -JB
(1) What is a Path?
A "path" in Google Earth is a series of vertices tessellated together to form a
line. In the KML code is a member of the <Placemark> family.
(2) Creating Paths
There are a number of ways to add KML objects in Google Earth. The three
simplest methods are:
(1) Use
the Menus (Add -> Path)
(2) Click
on the icon (showing three dots) in the Toolbar
(3)
Right-click on a folder in the Sidebar and select Add -> Path
When the dialog box appears move the cursor into the 3D Earth browser, and
click on the globe to create vertices. These will automatically become
connected by thin white line segments to create a path.
To change the thickness/color/opacity of the Path select options under the "Style, Color" tab in the dialog box.
Paths can also be automatically generated when importing GPS track logs (Tools
-> GPS…and select "KML LineStrings" as the output)
KML Examples
Earth’s Plate Tectonics – a file created by USGS uses Paths to delineate
plate margins
Mississippi River – the KML code has been modified
so that the blue line tracing the river turns red on mouse-over
Yellowstone NP’s roads – an example of a GPS file that includes a KML LineString
(Path)
(3) Editing Paths
To edit a path re-open the dialog box by selecting the path in the sidebar
(click on it so it is highlighted in light blue) and right-click (ctrl-click on
Mac). Select Properties (PC) or Get Info (Mac) at the bottom of the
menu that appears.
When the dialog box appears the vertices of the path will appear in the 3D browser as square red dots.
To Select a Vertex for Editing - Roll the cursor over the chosen vertex (it will turn green) and left-click on the vertex (it will turn blue)
- To Delete a Vertex – Select a vertex (see above) and press delete (or backspace)
- To Move a Vertex – Select a vertex (see above). Hold down the left-click and drag the
vertex to a new location
- To Add a Vertex – Select a vertex (see above) in at the segment of the path to add vertices to, and click in the 3D browser. If no vertex is selected, clicking in the 3D browser will add vertices to the end of the path.
(4) Using Paths
(a) Paths can used to create walls-like structures
Open the dialog box and select the "Altitude" tab. In the drop down menu change
Clamped to ground to Relative to ground, and make the
Altitude a value, e.g., 1000m.
(Note: In mountainous terrain not all the path will appear above the landscape if it is not raised high enough)
To create
the wall, select Extend path to ground. The color of this wall can now be
changed under the "Style, Color" tab (the values for "Area").
(b) Using Paths to generate automated tours
Any path can be used as the guide for a Driving Tour. Select the path in the
sidebar (click on it so it is highlighted in light blue), then press the play
button that appears at the end (right side) of the Places panel.
To change the settings for this tour open the preferences menu:
PC: Tools
-> Options -> Touring (tab)
Mac: Google Earth -> Preferences -> Touring (tab)
Change the values listed under When
creating a tour from a line.
*Tours will be discussed more in a separate
forum post*
KML Examples
Greatest Wall of China – An elevated path extended to the ground to create a "wall" (turn on "3D
buildings" to compare with a model of the real Great Wall).
National Mall Tour – Drive along the National Mall in Washington DC using the tour function. For optimal viewing turn on "3D buildings" and set the tour properties to Tilt Angle=80, Range=200, Speed=200.
Grand Canyon Flight – use of KML Tracks and a 3D
model (exported from SketchUp) to "fly" through the Grand Canyon (*Advanced KML*).
(5) Measuring Paths
The ruler tool (Tools->Ruler or icon in Toolbar) can be used to draw a line
that measures the distance between two points or the length of a multi-segment
path.
These lines can be saved as KML Paths.
The
length of a path that has been previously created is show in the "Measurements"
tab of the (editing) dialog box.
(Note: this last feature is the opposite
to what I stated during the tutorial and will require an up-to-date version of
Google Earth)
(6) Topographic Profiles
A topographic profile – a side profile graph that shows elevation changes along
a Path. They are created by selecting a Path (in the Sidebar), right-clicking,
and selecting Show Topographic Profile.
Topographic Profiles can be generated from any Path, regardless of how the Path was created.
KML Examples
Go With The Flow – an illustration of
how topographic profiles can be applied to the flow of rivers and understanding
drainage basins (*Note: this is still
developmental beta version*)
Gary Poole
Jeff's SpatialSci
Jeff Crews
Jeff Crews, Ed.D.
