For very sensitive applications, it may be necessary to adjust the spatial power spectral density (PSD), obtained by measuring any line figure on an optical surface, to eliminate the effect due to ground vibration. This is possible only if we know how to relate the standard random vibration output-numerous pointwise temporal PSDs-to spatial PSDs measured by interferometers. This paper serves as such a link. Two methods are presented here. The first uses direct integration starting from the mathematical definition of the spatial PSD of a function. The second borrows the relationship between two-dimensional spatial PSD and temporal PSD from atmospheric disturbance. As expected, both methods give nearly identical results.