Providing accurate pose estimation over time in various and unknown environments is a key component to the realization of autonomous missions where an absolute positioning system (like GPS) is not available. A lot of work has been done in that field where Simultaneous Localization And Mapping systems (SLAM) are still highly environment-dependent and computationally expensive. However, a major issue in SLAM solutions is the drift that appears in their odometry, due to error accumulation in the successive pose estimates. This may imply significant errors in the environment reconstruction or mission success. In this paper, a Nomadic and Accurate Positioning System (NAPS), based on the collaboration of mobile robots and their mutual sensing, is proposed. The originality and advantage of our solution is to provide a motion capture system with the nomadic ability. The result is environment-independent, computationally efficient, accurate and mobile. The system follows one or several mobile robots (explorers) and provides accurate positioning all along their mission. The NAPS is described as well as its moving process, and its accuracy is confirmed through a series of experiments, validating the whole approach.