Specular reflected light techniques, including both single wavelength and spectroscopic versions of ellipsometry and reflectometry, have been used for both etch and growth rate control. However, use of these techniques for process control on products has been limited due to the problems inherent in the analysis of reflected light from patterned structures. In this paper, we examine techniques for the quantitative analysis of data from both highly regular grating structures and from patterns with low local order. We find good quantitative agreement of vector diffraction theory to specular reflection data. We conclude that there is significant promise for the use of specular techniques for in situ monitoring of topography provided that computational speed issues can be improved.