unowned province reports?

[Merry Jolkar]

Each turn, I get reports about the disposition of troops in territories adjacent to my own (even without a scout). What determines the accuracy of these reports? Are they better for provinces near one of my castles? Do these reports become more accurate over time? How about if I DO have a scout in a region? Also, why is it that reports seem to revert to "no reports on this province"? Is there any way to have the most recent esimates remain? Do some scouts give more accurate information than others?

Thanks!
Merry