## Reference is needed for Optical flow sensor culculation through kalman filter

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Beginner
Posts: 4
Joined: Tue Feb 27, 2018 11:59 am

### Reference is needed for Optical flow sensor culculation through kalman filter

Hello every body ! I need Scientific Reference for Optical flow sensor calculation through kalman filter that is used in the following code
where does this equation come from? what is the reference for this !!

and thank you very much

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static void s t a t e E s t i m a t o r U p d a t e W i t h F l o w ( f lowMe asurem ent_t * flow ,
sensorData_t * sensors )
// ~~~ X velocity prediction and update ~~~
// predics the number of accumulated pixels in the x - direction
float omegaFactor = 1.25 f ;
float hx [ STATE_DIM ] = {0};
a rm _ m a t r i x _ i n s t a n c e _ f 3 2 Hx = {1 , STATE_DIM , hx };
predictedNX = ( flow - > dt * Npix / thetapix ) *
(( dx_g * R [2][2] / z_g ) - omegaFactor * omegay_b );
measuredNX = flow - > dpixelx ;
// derive measurement equation with respect to dx ( and z )
hx [ STATE_Z ] = ( Npix * flow - > dt / thetapix ) *
(( R [2][2] * dx_g ) / ( - z_g * z_g ));
hx [ STATE_PX ] = ( Npix * flow - > dt / thetapix ) *
( R [2][2] / z_g );
/ First update
s t a t e E s t i m a t o r S c a l a r U p d a t e (& Hx , measuredNX - predictedNX ,
flow - > stdDevX );
// ~~~ Y velocity prediction and update ~~~
float hy [ STATE_DIM ] = {0};
a rm _ ma tr i x _ i n s t a n c e _ f 3 2 Hy = {1 , STATE_DIM ,
hy };
predictedNY = ( flow - > dt * Npix / thetapix )
* (( dy_g * R [2][2] / z_g ) + omegaFactor *
omegax_b );
measuredNY = flow - > dpixely ;

arnaud
Bitcraze
Posts: 1832
Joined: Tue Feb 06, 2007 12:36 pm

### Re: Reference is needed for Optical flow sensor culculation through kalman filter

Hi and welcome!

The work was mainly done by Marcus Greiff during his Master Thesis. The report is there: http://lup.lub.lu.se/luur/download?func ... Id=8905299. See section 6.5.