This work extends a structural definition of location based on degrees of freedom (DOF) into an operational framework for detection, mapping, and analysis of structural accessibility. Location signatures are defined in terms of eigenvalue spectra and boundary characteristics derived from system response under controlled excitation. The framework demonstrates that structural variations can be identified through deviations in resolvable mode structure and associated boundary metrics, enabling representation of spatial variation as a field of accessibility-defined states. The analysis also explores the relationship between constraint geometry and observable structure. Full methodological and operational details are restricted pending further development.