In a modern, calculative world, the techniques of tracking are everywhere in the ascendant. Enhanced by algorithmic procedures and analytics, they have been incorporated into distributed network systems, augmented by new sensing and locationing technologies, and embedded into mobile devices, urban structures and environments. Simultaneously, new practices of tracking and sensing have emerged across the consumer, state and corporate sectors. These practices are amplified in the case of megacities as they strive to keep pace with rapid urban development. All movement (...) is subordinated to a condition of 'calculative mobilization’, whereby the urban realm is understood through the spatialization of algorithmic operations. And yet, due to their unique large- and multi-scaled accumulations of data-enhanced actors and their complex, stratified modes of proximity and interoperable relationality, the particular densities of megacities challenge conventional spatial formats of movement and positioning. This article offers new formats of analysis for these calculative practices and the agential and ontological status of the hybrid urban entities that they register and engender. It also offers new structuring principles and political orientations, which are particularly urgent as we witness the ascendance of 'Spatial Data Infrastructures’ (SDIs) that are often promoted as participatory and inclusive while remaining largely inaccessible, pursuing proprietary aims, and infused with the potential not only to protect and inform but also to violate. (shrink)