Integration of GPS data to estimate position and velocity

[matteo-meat]

Hello, me and some colleagues of mine are working on a Sensor Fusion project. Our setup includes an accelerometer, a gyroscope, a magnetometer and a GPS. We were able to use the first three sensors with the Madgwick AHRS library in C, and were starting to study a method to fuse also the GPS to the other sensors to have a better estimation of position and velocity, rather than using raw data from the GPS. Searching online we found different resources saying that the Madgwick filter could be modified according to our use case, but none of it included meaningful papers and/or code. We were wondering if you could please pinpoint us to some useful resources, be it papers or libraries, even better if based on this very same repository that we found to be very clean and well documented, thank you very much.