Finding a Hidden Camp?

[Amazing Mumford]

It's been a long time since our group used this, but it came up again-- where are the rules located for finding a hidden camp? The encounter guide for Forgotten Realms gives a percentage chance of an encounter vs. whether or not you have a regular camp or a hidden one... I assume it's probably some kind of Survival check, but what is the DC? Does anyone know where this rule is?

 

[archrai]

If you realy want to do that, i suggest to make a Survival check vs search check.
anyway, i think big size as a camp has to suffer -4 for each chart who stay there......