Blue Mountain
Dimensioning
The character is very good and determining the dimensions of an object or space. With a successful roll, they can determine if a room that looks to be 20 ft by 20 ft, is really that size or is really a foot or two shorter, which might indicate the presence of a hidden passage.

They are also good and determining volume. For example, if the character sees a pile of coins, then they can make a skill roll to know how many coins are in the pile.