Intuitive, reliable plans with contingencies: Planning with safety nets for landmark-based routing

We are interested in the problem of providing intuitive instructions for human agents to enable reliable navigation in unknown environments. Since the advent of GPS and digital maps, a common approach is to visually provide a planned path on a digital map defined in terms of actions to take at specific junctions. However, this approach relies on the agent to constantly and accurately localize itself. Furthermore, it comes in stark contrast to the way humans provide instructions-by leveraging known landmarks in the environment to both augment the description of the planned path as well as to allow to detect when the agent deviated from the planned path. Hence, there is need for assurable means of localization, an intuitive way of compactly conveying directions to agents and a systematic approach to account for human errors. To this end, our key insight is to employ known landmarks in the environment to overcome these challenges. We formally model this intuitive way to use landmarks for conveying instructions and for creating contingency plans. We present experiments demonstrating the efficacy of our approach both on synthetic environments as well as on real-world maps, computed using a smart-phone iOS application that we developed.