In MongoDB document, it is mentioned that a 2d Index uses 26 bits of precision.

Are these bits referred to the geohashed values that are stored on the index, or  mentioned for each dimension (x, y) individually (26 for x, 26 for y)? 

Also, a 2d sphere index is composed of geohash values which are fetched for a spatial query. Internally, what kind of operator is used for getting these values for a spatial query? (for instance i could image the $in operator).

Thank you,

Nikos