Parking assistance device an method of determining the length of a parking space

Single transmitters and receivers each have a transmitter (110-1-1) and receiver (110-2-2) and first (110-1-2) and second (110-2-1) pure receiving elements that each serve to receive reflected signals coming from sound fields in their associated transmitters/receivers, which are aligned in another receiving direction so as to facilitate the reception of reflected signals from other directions. Independent claims are also included for the following: (a) a method for determining the length of a parking space between a front and rear obstruction like vehicle in front of and behind a parking vehicle; (b) and for a computer program with program code to carry out the method of the present invention.