An example method includes determining a target area of a ground plane in an environment of a mobile robotic device, where the target area of the ground plane is in front of the mobile robotic device in a direction of travel of the mobile robotic device. The method further includes receiving depth data from a depth sensor on the mobile robotic device. The method also includes identifying a portion of the depth data representative of the target area. The method additionally includes determining that the portion of the depth data lacks information representing at least one section of the target area. The method further includes providing an output signal identifying at least one zone of non-traversable space for the mobile robotic device in the environment, where the at least one zone of non-traversable space corresponds to the at least one section of the target area.