I'm no rocket expert, but I have some ideas about altitude. > 1 - how do they measure altitude? GPS is notoriously poor at this. GPS is indeed notoriously ter

I'm no rocket expert, but I have some ideas about altitude. > 1 - how do they measure altitude? GPS is notoriously poor at this. GPS is indeed notoriously terrible. They might have better luck with it though, given they can buy high-quality receivers and always have a good view of the sky. However I think I read (or hope at least) that they use barometers. Even cheap smartphones have barometers for relative altitudes these days, and while the barometer data is influenced by the atmosphere and weather of the day (the focus of like all my startups [1]), the rocket could easily know about the differences in the weather and create MSLP (mean sea level pressure) numbers that would allow for excellent precision at landing. Your phone barometer can tell the difference in altitude between your head and your feet. [1] My latest go at this is https://www.allclearweather.com https://www.allclearweather.com (US, Android) with a goal of eliminating the altitude part of barometer data so that the remaining data can be QC'd, summarized with statistics and eventually hopefully included in weather models for increased forecast accuracy