This monograph is focused on the improvement of the modern navigation systems. In aeronautics high precision is very essential. Global Positioning System (GPS) has revolutionized the navigation systems. In this study GPS position measurements obtained from a GPS receiver, are improved using Kalman Filter based Satellite Distances method. The GPS receiver provides us with both available satellite positions and the position of the receiver. Using this information in the Kalman Filter a better position compared to the GPS receiver alone was aimed. In the monograph the integration of two navigation systems ADS and GPS was aimed. ADS is a widely used navigation system which measures static and total air pressure and the air temperature. ADS has high sampling frequency and poor accuracy, on the other hand, GPS has high accuracy compared to ADS but lower sampling frequency. Kalman Filter is used to integrate and minimize the errors of the two navigation systems. By this integration a navigation system with high sampling frequency and high accuracy is aimed. Another object is to calculate the wind speed with high accuracy, which is actually the error of Air Speed measured by the ADS.