But if there are a lot of gliders on route, without radios, without transponders, difficult to see at the best of times, and manoevering at variable altitudes, the chances of a midair seem high!
The accident statistics provide absolutely no support for that statement.
What use is it to give out continually changing gps position when altitude and direction are also continually changing? Not to mention the airwave clutter from tens of gliders all giving similar approximates!
Yes; exactly right. And the radio is already far too crowded already with people broadcasting long-winded position reports every two minutes (see generally
here).
Excellent post shortstripper.