EME Distances

[VK3PY]

I note that EME contacts are reported on the logger as great circle distances between stations, due no doubt to the intricacies of calculations involving grid squares. However, the respective stations' signals travelled a whole lot further, over an entirely different path. What's the great circle distance got to do with it?

Chas
VK3PY

[VK6KXW]

Hi Chas,
In a nut shell not a great deal; that system was put in place a long time ago and quite frankly is irrelevant
as it only applies to terrestrial signals as blind man can see.
Presumably put in place by the same guru's who keep the status quo by not allowing WSJT or now ROS for eme records.
At the present time I have worked k4rx on 6m eme which if ever the rules are changed will take out the
vk record.
Alas entrenched ideas prevent same.
Peter

[VK4GHZ]

What's the great circle distance got to do with it?

Nothing, but it provides a meaningful distance between the two stations.

Apart from any movement in the tectonic plates, the distances between any two points on the planet will always be fixed, unlike the moon itself.

At perigee the moon is 363,104 km away.
At apogee, the distance becomes 405,696 km.

You could calculate the position of the moon, and hence distance, but what would be the official distance?
Would it be based on station A or station B, or an overall average?

And where abouts on the moon did the signal actually reflect from?
That, you couldn't really know, and could skew the real distance by many thousands of km.