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Google Earth. Applications for Ham Radio. Radioactive Networks Pty Ltd. Darryl@radio-active.net.au. Who Am I?. Darryl Smith, VK2TDS, B.E. Self Employed Positioning Consultant Expert on Wireless Systems. The Talk. Introduction to Google Earth Applications for Ham Radio Tracking Weather

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Google earth l.jpg

Google Earth

Applications for Ham Radio

Radioactive Networks Pty Ltd

Darryl@radio-active.net.au


Who am i l.jpg
Who Am I?

  • Darryl Smith, VK2TDS, B.E.

  • Self Employed Positioning Consultant

  • Expert on Wireless Systems


The talk l.jpg
The Talk

  • Introduction to Google Earth

  • Applications for Ham Radio

    • Tracking

    • Weather

    • Path Calculations

    • GIS

  • File Format - KML

  • Implementing Applications

    • VB.NET

    • ASP.NET



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Google Earth - Licensing

  • Free to Non-Commercial Uses

  • $20/Year upgrade for GPS functionality, and route editing

  • $400/Year Commercial per seat

    • Movie Making - $200/Year

    • Premium Printing - $200/Year

    • GIS Data Import - $200/Year

    • Traffic Counts Data - $200/Year

    • Shopping Centre Data - $200/Year

  • Server Licensable Separately


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Applications for Ham Radio

  • APRS / Tracking

  • Weather

  • Path Calculations

  • GIS Applications


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History

  • Originally released as Keyhole Viewer by ‘Keyhole’

  • Most of the functionality was there in 2002, but Hardware and Networks were still lacking

  • Google purchased Keyhole in 2004, about the time of the DCC


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Example of User

  • Beyond Blue – a suicide prevention group for farmers in the Australian Bush organized a drive of vintage tractors through the Simpson Desert

  • They wanted to get community involvement so they set up a Google Earth feed showing their current position



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APRS Tracking

  • APRS Tracking is possible in Google Earth.

  • I have been importing APRS data into my own server software very successfully.


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Weather

  • Importing Weather Data into Google Earth from CWOP is fairly straightforward

  • Vectors can be added for wind direction and velocity

  • Graphics can show the rainfall

  • Icons can be used for Temperature

  • Graphs can be used to show trends

  • Text Boxes can be used to provide all data


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Image Import

  • Overlays can be loaded periodically, such as with weather radar data

  • These images can refresh automatically periodically

  • Custom datasets can also be used




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Path Calculations

  • Paths can be drawn on the map. These can be locked to the ground, or at a height. This can be done to model antenna paths.

  • Without extra software it cannot do fresnel zones


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Building Applications

  • Visual Basic

  • ASP.NET

  • PHP


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Google Earth Back End

  • KML, an XML variant is used to draw

  • KML is hierarchical

    • That is elements can be added at any point…


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File Format / Architecture

  • Essential Information :-

    • KML Tutorial

      • http://www.keyhole.com/kml/kml_tut.html

    • KML Specification

      • http://www.keyhole.com/kml/kml_doc.html


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Place a line…

Inside a Placemark

<LineString>

<altitudeMode>absolute</altitudeMode>

<coordinates>

-112.2550785337791,36.07954952145647,2357

-112.2549277039738,36.08117083492122,2357

-112.2552505069063,36.08260761307279,2357

-112.2564540158376,36.08395660588506,2357

</coordinates>

</LineString>


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Folders

<Folder>

<name>My House</name>

. . .

</Folder>


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Network Link

<NetworkLink>

<refreshVisibility>0</refreshVisibility>

<refreshInterval>121</refreshInterval>

<Url>

<href>//myServer/Googleearth/example.kml</href>

</Url>

<visibility>1</visibility>

<name>TestNetworkLink</name>

</NetworkLink>


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Two Types of Interface

  • Standard and ‘View’ based

    • Standard outputs data regardless of zoom level, area of display etc.

    • ‘View’ sends the extents of the view to the server whenever the data is downloaded.

  • View allows only appropriate data to be sent


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  • KML can point to a service. So if you pan around a map, when you stop, the service is asked to return a relevant KML file. It might, for example, take the bounding box of the area on screen and reach into a database to draw up data for that geography and place it on top of Google Earth.


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Example of a use of View Based output

  • Take the example of using GoogleEarth to display Weather Data.

  • Using the extents data you can determine the ZOOM level.

  • You can then send the NOAA Weather station data when zoomed out

  • Then as you zoom in CWOP stations are also displayed


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Building Applications A Simple KML File

<Placemark>

<description>Description</description>

<name>Server Name</name>

<point>

<coordinates>151,-34,0</coordinates>

</point>

</Placemark>


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Building Applications – VB.NET

Dim XTW as new XMLTextWriter (Filename, Nothing)

xtw.WriteStartElement("Placemark")

xtw.WriteElementString(“description”, “Description Text”)

xtw.WriteElementString("name", “Server name”)

Xtw.WriteStartElement(“point”)

Xtw.WriteElementString(“coordinates”, “151,-34,0”)

Xtw.WriteEndElement ‘point

Xtw.WriteEndElement ‘Placemark

Xtw.flush

Xtw.close


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Building Applications – ASP.NET

Private Sub Page_Load () Handles MyBase.Load

With Page.Response

.Clear(); .CacheControl = "no-cache“; .Expires = -1

.AddHeader("Pragma", "no-cache" & vbCrLf)

.AppendHeader("content-disposition",

"inline; filename=ge.kml")

.Write("<?xml version=“1.0” ?>” & vbCrLf)

line=“kml xlms=“http://earth.google.com/kml/2.0” >”

.Write (line & vbCrLf)

.WriteFile(“filename.kml" & vbCrLf)

.Write("</kml>" & vbCrLf)

End with

End Sub


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Building Applications – PHP - 1

  • <?php

  • $lat_int = rand(-90, 90);

  • $lat_dec = rand(0, 1000000000);

  • $lon_int = rand(-180, 180); $lon_dec = rand(0, 1000000000);

  • $lat = $lat_int.'.'.$lat_dec;

  • $lon = $lon_int.'.'.$lon_dec;

  • $response = '<Placemark>';

  • $response .= '<description>Generates a random placemark on each call to the server</description>';


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Building Applications – PHP - 2

  • $response .= '<name>Random KML server</name>';

  • $response .= '<visibility>1</visibility>';

  • $response .= '<Point>';

  • $response .= "<coordinates>$lon,$lat,0</coordinates>";

  • $response .= '</Point>';

  • $response .= '</Placemark>';

  • echo $response; ?>


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  • $coords = preg_split('/,|\s/', $BOX);

  • $bl_lon = $coords[0];

  • $bl_lat = $coords[1];

  • $tr_lon = $coords[2];

  • $tr_lat = $coords[3];

  • // calculate the approx center

  • $userlon = (($coords[2] - $coords[0])/2) + $coords[0];

  • $userlat = (($coords[3] - $coords[1])/2) + $coords[1];