[Paparazzi-devel] ACC_AMP value derivation in booz2_filter_attitude_cmpl_euler.c

[Avinash Rao]

Hi all,

I'm new to the mailing list and just wondering if anyone can help me with understanding how ACC_AMP is calculated in booz2_filter_attitude_cmpl_euler.c?

In the code, the following formula is used:

/* 
 * ACC_AMP
 * 9.81 * 2^10 * sin(pi/4) * ACC_AMP = pi/4 * 2^12 * F_UPDATE
 *
 */

and I understand from a previous thread (http://lists.gnu.org/archive/html/paparazzi-devel/2010-06/msg00014.html) that this is a linearization for the euler angle formulae:

phi = -atan(ay/az)
theta = asin(ax/|a|)

which is where the pi/4 / sin(pi/4) part would come from, however I'm unsure of where the other terms (2^10, 2^12, 9.81 (obviously gravity in some way!)) come from. Can anyone show me how this is derived?

Thanks very much in advance to anyone who can help.

Regards,

Avinash.


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Avinash Rao