function M=cp_M(imu_conf)
nsen=size(imu_conf,1);
M=zeros(nsen,6);
%Form M assuming full col rank.
for in=1:nsen
vr_a=imu_conf(in,4:6);
vr_a=vr_a/norm(vr_a);
if (imu_conf(in,7)==1) %accelerometer
M(in,1:3)=vr_a;
else %gyroscope
M(in,4:6)=vr_a;
end
end
%remove all-zero columns
nzr_col=[];
for in=1:6
if (sum(M(:,in)==0)==nsen)
%disp('cp_M: Zero col');
else
nzr_col=[nzr_col,in];
end
end
M=M(:,nzr_col);