The surface of seabed is affected by wave motion, current disturbance, sediment transportation and biological activities. Knowing the temporal change of the seabed, we can model the underwater acoustic scattering in more details. The scale of the features on the seabed varies from meters for large sandwaves, and down to less than one millimeter for the prints left by biological creatures. For measuring small scale roughness of seabed, laser scanning is one of the methods commonly used. In this work we study the performance of the laser scanning by analyzing the results measured from a known test piece as ground truth. The surface is obtained by realization of a power spectrum which contains two parts: a Gaussian component that gives the ripples and a power-law component that gives small scale roughness. Using the parameters estimated from a real seabed, a 60 cm by 40 cm test piece is machined to have a ripple wavelength of 20 cm, rms height of 4 mm, and sub-mm roughness on its surface. The test piece is fabricated with given surface data points by a computer numerical controlled (CNC) milling machine accurate to the order of 0.25 mm. Measurement of the surface data are converted to spatial spectrum space for comparison with the model. Preliminary results indicate that intensity of the roughness spectrum measured the laser scanning matches closely with the model from wavelength around 20 cm down to 6 mm for both along and across ripple directions