An integrated navigation system for improving the vertical positioning accuracy of barometric altimeter enhanced GPS was proposed. The state and observation equations were established based on the location error of GPS,height error of BA and their “current” statistic model. The data fusion algorithm was given by iterative Kalman filtering(IKF). The theoretical analysis simulation and test results indicated that the vertical positioning accuracy, performance，reality and availability are improved more efficiently by the IKF algorithm than Kalman filter. The safety and reliability of airplane in the process of near-enter is guaranded by the algorithm which can be used as a guide system for precision approaching and landing.
