Abstract—We are concerned with enabling truly large scale autonomous navigation in typical human environments. To this end we describe the acquisition and modeling of large urban spaces from data that reflects human sensory input. Over 181GB of image and inertial data are captured using head- mounted stereo cameras. This data is processed into a relative map covering 121 km of Southern England. We point out the numerous challenges we encounter, and highlight in particular the problem of undetected ego-motion, which occurs when the robot finds itself on-or-within a moving frame of refer- ence. In contrast to global-frame representations, we find that the continuous relative representation naturally accommodates moving-reference-frames – without having to identify them first, and without inconsistency. Within a moving-reference-frame, and without drift-less global exteroceptive sensing, motion with respect to the global-frame is effectively unobservable. This underlying truth drives us towards relative topometric solutions like relative bundle adjustment (RBA), which has no problem representing distance and metric Euclidean structure, yet does not suffer inconsistency introduced by the attempt to solve in the global-frame.