The barometer alone, won't serve much as that is very unreliable and prone to a wide range of ambient disturbances or measurm. errors. TO make a decent altitude hold I need and want something more robust, which the barometer alone cannot give me.
Extensive writeup:http://home.earthlink.net/~david.schultz/rnd/2004/KalmanApogeeII.pdfI took a lot of math in college but not enough to grasp all of this.
I have a barometer that give me the altitude estimation but this is not enought because barometer have some drift and the sample rate is not enought fast for have a good stabilization so i thought to fuse the accelerometer z axis with the barometer datas for have a clean and fast altitude estimation.