Google Earth Options in HDPath™
Q: How can I improve the path profile exported to a KML file for Google Earth?
A: With TAP6.0.2342 or later, including the 3DDisplay Module and a Maintenance Subscription date of June 30, 2010, or later, you can use several options to improve the profile in Google Earth.
Note that all values in this example are for demonstration purposes only. You should determine appropriate settings for your application.
This article describes additions to the Google Earth Export function in HDPath. More information about the basic operation is described in Path Profiles in Google Earth. You can also draw multiple paths in Google Earth. The Google Earth Path Markers article describes how to add a line with distance marks along the ground.
The earlier option to export a path profile to a KML file for Google Earth displayed the line of sight and three boundaries for the Fresnel zone – directly below the line of sight path, and to the left and right of the line of sight path:
The updated version allows you to create a mesh to display the entire Fresnel zone region to better visualize the effect of obstructions along the path:
This more complete representation of the Fresnel zone gives you more flexibility to explore and display the effect of obstructions on the path.
You can download a sample .KML file for this path if you want to see the effects in Google Earth. Click the link, then use the Edit-SaveAs menu in your browser to save the file.
(Note that the reason the Fresnel zone in these images appears elliptical rather than circular is because the Google Earth Tools, Options menu was set to set the “Elevation Exaggeration” to a factor of 3 to provide more definition of the terrain features. The vertical dimension of the Fresnel zone is stretched to match that exaggeration.)
Note that since the image from the new version is more complex it will take longer to create. A message will be displayed during the process:
To use the function to draw additional lines for the Fresnel zone around the line of sight, click the “Configuration” menu in HDPath, then click “Google Earth”, then select “Fresnel Angles”
A form will be displayed to specify the starting and stopping angles where Fresnel zone lines will be drawn around the line of sight, and the step, or increment, between those lines:
(The angle around the line of sight is the angle looking at the transmitter from the receiver end, incrementing clockwise.)
The Fresnel zone can also be drawn as a “mesh” by checking the “Fresnel mesh” item in the “Configuration|Google Earth” menu.
Without the “mesh” effect, only the Fresnel lines are drawn:
Adding the mesh provides further definition for the Fresnel zone around the line of sight:
An adjustment in the display of the earh curvature must be made to export the path profile to the KML file for use in Google Earth. In the earlier version a message was displayed each time describing this adjustment.
In the new version, you can mark the “Always bend LOS and Fresnel” option in the Configuration menu to eliminate that message.
In the earlier version the path was drawn and the initial viewing angle in Google Earth was above the path, with the map oriented normally with north at the top:
You can use the Google Earth zoom, rotate, and tilt controls to change the view of the path.
In the new version, you can select two other viewing angles, from the Transmitter to the Receiver, or the reverse path. Under the Configuration menu, click Google Earth, then “Initial View Location” and the desired view:
This gives a starting point for using the tilt, zoom, and pan functions in Google Earth.
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