Hi John,
I don't know if you're already aware, if you go into Preferences, you can set radar rings to either centred on Home, or at centre of map then by zooming in and out it is possible to use these as a rather crude measuring tool in nautical miles (1 NM equal to 1.15 Imperial Statute mile). If centred on home you can work out how far away from you a A/C is, and this line if sight distance is also shown in one of the columns. If I'm trying to teach granny to suck eggs, I apologise, but moving the 'floating' rings is how I guestimate distances - and fairly accurately +/- 5% usually. By zooming in and out you can also use these rings to measure line of sight land distances. HTH Jon