Tracking stops at French coast


I can see aircraft as far out as the French/Spanish/Belgium coast, but not over land.

Why might that be? I’m near Gatwick, I’m seeing aircraft almost 200NM in the opposite direction, toward Wales and beyond.

Seem strange to see nothing over the European mainland.

What might be the reason for this?


more than likely there is something in the way.


A salt water path is better for RF signals than land. It could be a factor as well.


Gatwick to the nearest point on the French coast is only 70 nautical miles, so as somebody above said so succinctly; there is something in the way.

You can determine your radio horizon using the web site, there is plenty of info on this site that has been posted by abcd on how to use it.

Note that it uses the physical topography and doesn’t allow for obstructions such as buildings and trees. My theoretical coverage in one direction is beyond 250nm, however actual range is nearer 75-100 purely due to large and dense non-deciduous trees.

The English Channel may potentially affect signals due to variations in the lower atmosphere, and that wouldn’t matter if it were saline or fresh water, but it won’t be a barrier to receiving signals.



What is the Maximum Range I can Get?

Using aproximate latitude/longitude (51.11, -0.15) given at “My ADSB” page of user richardlawes, I have done a maximum range plot. This plot shows that the natural topology restricts the maximum range to only a thin coastal strip of northern Europe, that also for high-flying planes at 40,000 feet (blue curve). Planes flying at 10,000 feet can be seen up to midway across English Channel (yellow curve).


Using those co-ords the following shows the elevation for the path to the coast at Dungeness. Vertical scale is rather exaggerated, but it shows how the height and the proximity of the South Downs are having a negative effect on range.(Coast is on the right hand end of the graphic)