1. A method of determining a location within a physical structure comprising: storing a model of a physical structure comprising a plurality of nodes connected by a plurality of struts, each of the nodes and struts of the model corresponding to respective nodes and struts of the physical structure; assigning a non-unique identifier (ID) to each node of the model according to a pseudo-random sequence, wherein each node of the physical structure encodes the non-unique ID assigned to the corresponding node of the model; receiving a set of non-unique IDs encoded onto respective nodes of a contiguous subset of nodes of the physical structure; locating a set of non-unique IDs in the model corresponding to the received set of non-unique IDs; and determining a location in the physical structure from the located set of non-unique IDs in the model.