# alingc_std_v001

```%Standard methods.
%Cbn_est=(I-S(e))Cbn, e=E[acc_err;ref_err]
%%TODO: The argument names became meaningless. I need to revise this.

function [Cnb E]=alingc_std(acc, ref, Llh, mtd)
E=[];
if (mtd==0) %gyroscompass
%normalize acc and gyro;
gyro=ref;
acc=acc/norm(acc);
gyro=gyro/norm(gyro);
cL=cos(Llh(1));
sL=cos(Llh(2));
Cnb=[cross(acc,gyro) gyro acc]*[0 -1/cL 0;1/cL 0 0;-sL/cL 0 -1];
elseif (mtd==1) %Rogers, Titterton etc (gyrocompass)
[Rn, Re, g, sL, cL, WIE_E]=geoparam_v000(Llh);
gyro=ref;
Cnb=[cross(acc,gyro) gyro acc]*[0 -1/cL/WIE_E/g 0;1/cL/WIE_E 0 0;-sL/cL/g 0 -1/g];
elseif (mtd==2) %ref is any vector in the x-z plane (could be gyro or compass output (ignoring declination or aligning to mag north))
nref=norm(ref);
nacc=norm(acc);
vr_z=-acc/nacc;
vr_y=cross(vr_z,ref/nref);
nvr_y=norm(vr_y);
vr_y=vr_y/nvr_y;
vr_x=cross(vr_y,-acc/nacc);

Cnb=[vr_x vr_y vr_z];

%Error matrix (completely ignores the effect of norm errors. (hence, not
%so correct)
E=zeros(3,6);
E(1,1:3)=(Cnb(:,2)/nacc)';
E(2,1:3)=(-Cnb(:,1)/nacc)';
E(3,4:6)=(cross(Cnb(:,1),acc/nacc)/nref/nvr_y)';
E(3,1:3)=(cross(Cnb(:,1),-ref/nref)/nacc/nvr_y)';
end
end
```