How would we tell ? 12 - 15miles is not very far at all. I am not sure I would have thought radiation greater than 0 degrees is not a ground wave... it travels in space not the ground. Of course through every object in its way, houses, cars, street furniture, shops etc. etc.
"Ground Wave propagation uses the area between the surface of the earth and the ionosphere for transmission, it is a method of radio wave propagation. Ground wave propagation is also called surface wave propagation. The ground wave follows the contour of earth and hence it can propagate considerable distances."
That is a definition I got online, the first one that appeared. That is rather a large scope for what a ground wave is. That seems to suggest that ground wave is anything before an ionospheric refraction.
I have no horse in this race really... I had it in mind ground wave somehow conducted through the ground itself for a relatively short distance unless wavelength was very long..
Here this suggests 3 parts to a ground wave.. basically anything that is not a refraction from ionosphere
https://www.electronics-notes.com/articles/antennas-propagation/ground-wave/basics-tutorial.php
So I guess 11m does also have ground wave by those definitions. I am open I don't have a fixed position just as interested in passing as anyone else really.
I would have thought if a wave front is in contact with ground and is also a direct wave on any given path, that the direct wave would be a greater proportion of the received signal as the earth conducted wave would be greatly attenuated, relatively. Unless there were massive obstacles for the "space" wave to get through as well.
It does rather seem this is just a discussion on semantics.
