Basically there is a thin layer around the aircraft in which it feels like static pressure - a good way to demonstrate is put your hand out of the window in a moving car and put it flat against the door, you will feel no dynamic pressure, only static. Hence, static ports are usually small holes on the side of the fuselage.
To measure the PITOT or toal pressure, the Pitot tube must stick out far enough so it it outside this static layer. Remember that PITOT (total) pressure is dynamic pressure PLUS static. For altitude read out you need static pressure, for airspeed you need dynamic, dynamic pressure is created by the movement through the air.
Last edited by RTN11; 18th Oct 2012 at 20:14.