The invention relates to location determination apparatus for determining a location of a first object (2) like a catheter within a second object (3) being, for example, the heart of a person. The first object comprises a first ultrasound unit, and a second ultrasound unit (5) is located outside the second object. A location determination unit determines the location of the first object within the second object based on ultrasound signals transmitted 5 between the first ultrasound unit and the second ultrasound unit. This allows determining the location of the first object within the second object reliably in a way which is an alternative to using a transmission of electrical signals for determining the location and which may lead to an improved accuracy of determining the location.