Motivation for the investigation of a high precision position estimation system and an autonomous landing algorithm is the demand for Unattended Aerial Systems (UAS) capable of fulfilling e.g. surveillance tasks in contaminated or in inaccessible areas without any assistance of a human pilot. Hence, this paper deals with the development of a Wireless Sensor Network (WSN) based system for 4 Rotor Helicopters able to locate an Unattended Aerial Vehicle (UAV) with an accuracy of a few centimeters. Such systems are needed for high precision autonomous landing tasks.In the following chapters the position estimation system using a WSN is described. Many measurements were done to show the accuracies of the different methods. Further, the autonomous landing strategy was implemented on a flight demonstrator for validation and experimental results are provided.