FlightAware Discussions

Google Earth line of sight how-to

This may have been posted before, but for those who have access to Google Earth Pro, there is some useful functionality in exploring line-of sight signal paths. I think most of us have explored the “Hey Whats That” plots to see what we can expect in terms of ADS-B reception, but this link details some interesting things that can be learned using Google Earth Pro for specific points around your location.

This site is geared towards those thinking of creating their own ISPs but I thought the following was a useful tutorial: https://startyourownisp.com/posts/guide-to-google-earth/ , starting at “Line of Sight”.

The Elevation Profile function clearly illustrates some of the location challenges in perspective.

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Messing around more with this I have come to understand the fundamental difference between the Hey Whats That data versus what you can see using the Google Earth line of sight function, (especially if you use the Lines with different heights function described in the above link) :

HWT shows you the theoretical line of sight without houses, trees, etc. whereas using the Google Earth line and zooming in you can actually see those elements and how they may impact line-of sight. Everyone generally knows whats right by their location, but its particularly helpful to know if theres taller things just out of visual range that may block signal at a given height and range. The closer those things are, even if they aren’t truly large, the greater impact they have in terms of the degrees of horizon azimuth blocked and at what altitude.

Of course the line of sight blocked doesnt necessarily mean RF blockage, but more often than not its an issue.

Apparently an antenna raised to 200 feet will solve most of my issues, if not my marriage. :smile:

It’s worth noting the different data sources involved - heywhatsthat uses data from the Shuttle Radar Topography Mission which has coverage inside 60° latitude (the shuttle orbital inclination for that mission) and a resolution of about 30m, and somewhat worse outside the US. Since it is data generated by radar, the height recorded will be affected by the radar reflectivity of whatever is on the ground, so in a city it may not be exactly at ground level. Larger isolated buildings probably don’t have too much effect because of the lower resolution.

The areas of Google Earth which are available in 3D are created through a mixture of LIDAR and photogrammetry via aerial survey, and have a very much higher resolution. The base topography used is Google Earth is also based on SRTM data, though it has been added to and refined with a variety of sources over time.

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Thanks for that info- I forget that depending on where you are on Earth, the resolution/ image quality of the satellite imaging for all of these tools may vary from awesome to awful.