The Survey Says:

The building corners are established using a transit, working off established known locations, such as marked property corners, or better yet, a City benchmark:

Then stakes are set to mark each corner of the house.

Offset stakes are set with steel pins at a set distance (10' in our case) outside the excavation area.  The offset pin is marked with a tall white stick in the below photo.  The steel pin itself has a pink ribbon around it.  When the hole for the house is dug, the stakes marking the house corners must be removed.  They are reconstructed in the excavation by using these steel pin offset stakes as a reference.