The spreadsheet looks really nice...you have some pretty good Excel skills. Here comes the hurt: you can't do velocity differentiation from altimeter data without huge amounts of error. Plain and simple. I've tried it, others have tried it and came to the same conclusion. When you differentiate the altitude to get velocity, the error between each data point sticks out....unlike integrating accereation, which "smooths out" the error between each data point.

Do you see the "up and down" nature of the Perfectflite: Altutude goes up, stays there for a few samples, goes up again, stays there for a few more samples, repeat. This is destruction for differention subroutines. You get a positive velocity, then 0 velocity, then positive velocity again. Sure, you could average the data points, but that takes out all of the large changes in position, making your velocity innacurate.

To prove my theory that baro altimeters suck for velocity calculations, I flew two perfectflite MAWD's and an ARTS accerometer in the same rocket. When I plugged it into you spreadsheet, I get about 680 MPH for max velocity, which is a little under .9 mach. Compare that to the ARTS data, which shows that it hit 593 MPH. Big difference. Add to the fact that the ARTS samples at 200Hz, but the MAWD samples at 20Hz, the ARTS will give you good data, while the MAWD will give you total junk, no matter what you do with it. I get an average of 20% error on every flight, making it useless for "mach busting" calculations.

Nice try, but so far as I can tell, it can't be done. Spend an extra $100 and buy an ARTS, there is much more data to mess around with.....it's a bundle of fun.