An Inertial Navigation System (INS) can individually produce the navigation data, i.e position, velocity, of the vehicle. However, a large amount of error is introduced by INS sensors resulting in an unacceptable drift in the output positioning data. Therefore, in most cases external aids are employed to correct the output of INS. Using these aids, an integrated navigation structure is developed to produce accurate positioning data. In an integrated navigation system, INS output is used to calculate current navigation states and external navigation systems supply further measurements. Various aided navigation systems are employed in the state of the art integrated navigation systems to provide the most probable corrections to the estimated state. One of the integrated navigation systems is Terrain Aided Navigation (TAN). TAN is a technique to estimate the position of a moving vehicle by comparing the measured terrain profile under the vehicle to a stored Digital Elevation Map (DEM). Several TAN techniques are proposed in the literature which can be align="left" dir="LTR" Keywords: Inertial Navigation, SONAR, TERCOM, Kalman Filter, SITAN An Inertial Navigation System (INS) can individually produce the navigation data, i.e position, velocity, of the vehicle. However, a large amount of error is introduced by INS sensors resulting in an unacceptable drift in the output positioning data. Therefore, in most cases external aids are employed to correct the output of INS. Using these aids, an integrated navigation structure is developed to produce accurate positioning data. In an integrated navigation system, INS output is used to calculate current navigation states and external navigation systems supply further measurements. Various aided navigation systems are employed in the state of the art integrated navigation systems to provide the most probable corrections to the estimated state. One of the integrated navigation systems is Terrain Aided Navigation (TAN). TAN is a technique to estimate the position of a moving vehicle by comparing the measured terrain profile under the vehicle to a stored Digital Elevation Map (DEM). Several TAN techniques are proposed in the literature which can be align="left" dir="LTR" Keywords: Inertial Navigation, SONAR, TERCOM, Kalman Filter, SITAN
