  We develop a novel interferometric technique to measure small angular and
lateral displacements of an optical beam. The technique relies on the
metrological performance of the Hermite-Gaussian $HG_{m,0}$ spatial modes. We
report an improvement factor of $41$ in the signal-to-noise ratio, as compared
to the Gaussian mode, using modes as high as $m=20$. This considerably enhances
the sensitivity of such measurements and attests its efficiency.
