disclosed herein is a method of constructing an environmental map using sonar sensors . the method includes the steps of checking whether conflict cells have occurred using input sonar sensor data ; if conflict cells have occurred , selecting incorrect data and eliminating the conflict cells using sound pressure comparison until the conflict cells do not occur any longer ; and once the elimination has completed , preparing a grid map using a maximum approximated likelihood approach . inconsistency in data occurs when multiple pieces of sensor data overlap each other , the conflict cells are cells that experience inconsistency over an entire arc region , and candidates for the incorrect sonar sensor data are obtained when the conflict cells occur .