Simultaneous determination of the sound speed field and of the position of the acoustic elements is an important possible in ocean acoustical tomography. The problem is examined here in the range independent case, with axial transmitters and receivers. After showing that moving the receiver by a few kilometers does not compromise the ray identification, an inversion is performed for both a fixed and a moving receiver. Allowing receiver displacements does not reduce the resolution significantly in the upper part of the ocean but does increase the sensitivity to noise. This sensitivity implies that for such experiments the measurement of the travel times must b very accurate. More efficient use of a priori knowledge of the ocean reduces this sensitivity by decreasing the number of degrees of freedom.