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NNTP-Posting-Date: Sun, 11 Dec 2016 04:57:20 -0600
From: Gareth Owen <gwowen@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: Mars lander crash
References: <o2e7s1$ea6$1@dont-email.me> <o2e8sg$hp7$1@dont-email.me> <o2ecu8$v73$1@dont-email.me> <91e540d9-f110-4665-912d-5200cc0bc104@googlegroups.com> <o2ek4p$q0s$1@dont-email.me> <a05589b4-42a9-447e-8f8d-648a8ec88910@googlegroups.com>
Date: Sun, 11 Dec 2016 10:57:20 +0000
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Xref: csiph.com comp.lang.c:98774

already5chosen@yahoo.com writes:

>> 2) How can you explain (if it wasn't an overflow) that the height 
>> changed sign?
>
> Result of Kalman filter or of similar algorithm. Taken uncritically by
> the rest of program logic.

Doesn't even have to be anything as complicated as a Kalman filter.

If you say

delta(estimated_height) = estimated_velocity * delta(t)

then an overlarge (saturated) descent velocity reading will cause delta
height to become large and negative.