For some time I have noticed that on the statistics page, the reported distance of a plane from feeder does not correlate with what I see on the FA map plot … at least when “nm” is my chosen unit.
Today, my feeder was reporting a plane which was tracking tangentially just beyond the 120nm ring. I estimated its distance to be 125nm. However, in the “Recent flights with positions from this feeder on FlightAware.com” table, the distance was reported as quite a bit more than that.
I have also noted that when the same table reports a plane being reported by my feeder in say, the 120-160nm bin I sometimes don’t get credited with those positions in the “Positions Reported by Distance from Receiver” table and chart.
So using the lat/lon of my feeder and the lat/lon of the position report I calculated the distance and confirmed the discrepancy. The stats page seems to be reporting distance from feeder in statute miles because when I apply the 1.15 conversion factor all seems well with the world.
(While we are on the topic, the units “km” in the header of the “Nearby ADS-B sites” table should be removed.)
Anyone can confirm the anomaly by choosing statute miles as their units then checking distance of a plane from the receiver, then switching to nautical miles and checking that same distance. The distance reported does not change.