This is how I did it, by hacking around just three files.
I’m finding it it useful to spot signs of Tropospheric lift/ducting.
The elevation angles start going negative and highlight targets that are lower than one would normally be able to observe.
I’ve written the instructions here…
…if anyone is interested giving it a try.
I like this. I don’t use SkyAware but I like the idea of this.
Some signs of Tropo for me here this morning:
The elevation angles are way down on what is normal for me from my site with 361ft asl antenna.
I’m currently seeing traffic beyond my normal horizon to the North/ NE
Craft which would normally need to be at 40,000ft to be seen are being seen at under 6,500ft.
The elevation angle column enhancement is working nicely for me 
Update: Confirmed observation of extra ADS-B range
Cool addition! So negative elevation angles basically mean they’re out of line of sight?
I’ll take a look at the modifications and look into adding it in our next release.
