A system includes a computer that includes a processor and a memory storing instructions executable by the processor to decompose a stored map of an area into a plurality of polygonal sub-areas. The instructions include instructions to generate a set of target locations in the polygonal sub-areas according to a leaky ball algorithm. The instructions include instructions to actuate a robot to move to a first one of the target locations of the set. The instructions include instructions to actuate a sensor to collect data at the first one of the target locations.