This paper presents applications of GNSS simulation from system analysis to application development. Many examples are given where the the Galileo System Simulation Facility (GSSF) has been used. Therefore a brief introduction of the GSSF is given including the validation approach used, its use in system analysis, application development support, GNSS training, and exemplary GNSS analysis results for Turkey. In the following sections examples for GNSS simulation applications in the areas system validation, aviation, road traffic, application development and test ranges, and indoor navigation and logistics are described based on projects.