The demand for unattended aerial aystems capable of fulfilling e.g. surveillance tasks in contaminated or inaccessible areas without assistance of a human pilot is the motivation for the investigation of a high precision position estimation system and an autonomous landing algorithm. Hence, this paper describes the development of a wireless sensor network (WSN) based system able to locate a quadrocopter with an accuracy of less than 5 centimeters. Such systems are needed for high precision autonomous landing tasks. Several measurements show the accuracies of two different methods, a radio- and an ultrasonic-based measurement system. Furthermore, an autonomous landing strategy was implemented on a flight demonstrator for validation and experimental results are provided.