I have been developing models of the ionosphere for some time, but recently, I've been asked "What constitutes sufficiently accurate foF2?" The URSI standard for foF2 scaling from an ionogram is 5d, where d is the frequency resolution of the ionosonde in the vicinity of foF2. Others have mentioned accuracy standards ranging between 0.5 MHz and 1.0MHz. My question is, is there a consensus within the field on the generally required accuracy of foF2? If it is application-specific, what are the necessary accuracy levels for these various applications?

In any responses, please provide references to support your point of view.

I look forward to an interesting and productive discussion.