A method, including capturing, from an imaging system, athree-dimensional (3D) image of a body cavity, and using thecaptured 3D image to construct a simulated surface of the bodycavity. A probe having a location sensor is inserted into thebody cavity, and in response to multiple location measurementsreceived from the location sensor, multiple positions aremapped within respective regions of the body cavity so as togenerate respective mapped regions of the simulated surface.Based on the simulated surface and the respective mappedregions, one or more unmapped regions of the simulated surfaceare delineated, and the simulated surface of the body cavity isconfigured to indicate the delineated unmapped regions.
