Research on cooperative robotics has increased radically over the past decade due to its simplicity and applicability in a variety of fields. Shape formation plays an important role in such cooperative behavior. Our work deals with the formation of a circle by a group of mobile agents (robots) that initially are randomly spread and randomly oriented in an unmapped terrain. The agents have simple characteristics and limited capabilities. They are autonomous, homogeneous, anonymous, and memory-less. They do not communicate with each other, but are able to measure the inter-agent distances and angels. The agents follow the same distributed algorithm synchronously without any central control. The existing algorithms make it necessary to scan all the agents over the whole terrain. The main advantage of our algorithm is that each agent makes use of local information collected from two neighboring partners. Our algorithm also results in a regularly distributed circle for any form of initial distribution. By changing a parameter in the algorithm, the circle can either be made to grow or shrink uniformly. Applications of this work can be made to a variety of areas such as space missions, military operations, in agriculture and fire fighting
