In VMC regular position calls are not given - if we all did that for each change of heading (we follow the energy in the air) then any general frequency would be swamped on a reasonable soaring day.
In IMC a call is given before entering cloud giving:
- Callsign
- 'Entering cloud at' a position relative to a prominent named feature on the 1:500,000 chart
- Height ASL.
Subsequently calls are given about every 500 ft change in height, more frequently if two gliders are sharing the same cloud to maintain vertical separation.
A further 'clear of cloud' call is given when in VMC.
Regarding listening watch, gliders have only one COM radio, and in IMC the highest risk is from another glider, and so the common glider cloud flying frequency (130.400) is used. I suspect using another flight information area frequency would not be welcome, and given the areas where several different possible frequencies exist, no guarantee that two gliders wishing to use the same cloud would find themselves on the same frequency.