It really depends on three factors, as to whether you will find stuff or not. Actually, make that four. "Encampment" is a tricky word to begin with. Are we talking about an army, an army corps, a regiment, squad or whatever. Apparently the more men, the more area they covered. There are US army regulations some of which have been posted here on Tnet about how far apart winter huts were to be, but a lot of the war literally hit and run, so it will depend on your site.
Knowing the size of the units involved is the first thing. The second is how long were they in a spot and were they resupplied while there. That last piece may be almost impossible to know. Now in the Orange and Culpeper County camps (VA) from both armies, yes they were resupplied throughout that winter. Then they moved on, never to come back. At Winchester, VA, the land changed hands so many times it was incredible and both sides were reinforced and resupplied.
The armies never camped long term too far from a fresh water source. At two placed I dig the water sources are small creeks. Both camps are more than 100' from the creeks, most likely due to the possibility of flooding and their wanting to avoid that.
Using maps, documents and histories of the area you want to dig is important, but also thinking out of the box is also important. If it's in a history book anywhere, someone has probably already dug there. Even during the Civil War the locals would scavenge battlefields, especially for lead, which was quite valuable back then.
My three best spots I have ever found for Civil War relics were places not mentioned in the history books, but places that were close by.
The first, just along a supply route and along one of the major roads Jeb Stuart made one of his famous rides on.
The second, a large plantation, not known for Civil War at all, but along a road soldiers retreated on.
The third, a mile away from a hilltop the Confederates were known to have been watching the railroad from. The hilltop they were supposed to be on, well, we did detect there and found NOTHING. Now, where the troops stayed was a mile away, out of the line of sight of the railway and town and near a water source. That spot was found by accident.
So...think out of the box, and look for connecting roads, houses now long gone, old crossroads and rail lines.
