function [s] = initState(start, yaw)
    % Initialize 13 x 1 state vector

    s     = zeros(13, 1);
    phi0   = 0.0;
    theta0 = 0.0;
    psi0   = yaw;
    Rot0   = convertRPYtoRot(phi0, theta0, psi0);
    Quat0  = convertRotToQuat(Rot0);
    s(1)  = start(1); % x
    s(2)  = start(2); % y
    s(3)  = start(3); % z
    s(4)  = 0;        % xdot
    s(5)  = 0;        % ydot
    s(6)  = 0;        % zdot
    s(7)  = Quat0(1); % qw
    s(8)  = Quat0(2); % qx
    s(9)  = Quat0(3); % qy
    s(10) = Quat0(4); % qz
    s(11) = 0;        % p
    s(12) = 0;        % q
    s(13) = 0;        % r
end
