A position sensing and map generating unit, comprising: a mapping instrument having a position element and operable to be located in a volume, wherein the mapping instrument includes at least one of: an inflatable portion, or at least two electrodes (108,110) operable to sense a voltage as the position element; at least a first pair of axis generation electrodes (46, 48, 50) positionable on an exterior surface of the volume; a driver operable to inject a current between the first pair of axis generation electrodes to generate an axis current within the volume; a position determination processor operable to determine at least one position of the position element from a voltage sensed by the position element, wherein the voltage is caused by the axis current; a storage system operable to store the at least one determined position; a display device operable to display a map based on the at least one determined position, wherein the map is created from one or more points regarding the at least one determined position, wherein the map represents at least a surface of the volume and is displayed with the display device for visualization by a user based solely on the at least one determined position; and a display processor operable to augment the map displayed with the display device, characterized in that the display processor is further operable to: render a filled volume; determine a disturbed volume including a subtracted region by removing points regarding determined positions from the filled volume; and display the subtracted region as a selected geometry relative to the disturbed volume with the display device. a mapping instrument having a position element and operable to be located in a volume, wherein the mapping instrument includes at least one of: an inflatable portion, or at least two electrodes (108,110) operable to sense a voltage as the position element; an inflatable portion, or at least two electrodes (108,110) operable to sense a voltage as the position element; at least a first pair of axis generation electrodes (46, 48, 50) positionable on an exterior surface of the volume; a driver operable to inject a current between the first pair of axis generation electrodes to generate an axis current within the volume; a position determination processor operable to determine at least one position of the position element from a voltage sensed by the position element, wherein the voltage is caused by the axis current; a storage system operable to store the at least one determined position; a display device operable to display a map based on the at least one determined position, wherein the map is created from one or more points regarding the at least one determined position, wherein the map represents at least a surface of the volume and is displayed with the display device for visualization by a user based solely on the at least one determined position; and a display processor operable to augment the map displayed with the display device, render a filled volume; determine a disturbed volume including a subtracted region by removing points regarding determined positions from the filled volume; and display the subtracted region as a selected geometry relative to the disturbed volume with the display device.