This report presents integrity monitoring and integration methods for an Inertial Measurement Unit (IMU) and a gps receiver. The methods are applied to data from a Maxus sounding rocket used for microgravity research. It is crucial to determine the rocket position during launch to ensure a safe landing location. Today, the navigation relies on IMU integration only. Involving a GPS receiver enhances the position accuracy but there is a need for protection against faulty satellite range measurements. Monitoring over a sequence of the measurements gives higher confidence to the tests.