  Analysis of the spatial dependence of current-voltage characteristics
obtained from scanning tunneling microscopy experiments indicates that the
charge density wave (CDW) occurring in NbSe$_2$ is subject to locally strong
pinning by a non-negligible density of defects, but that on the length scales
accessible in this experiment the material is in a "Bragg glass" phase where
dislocations and anti-dislocations occur in bound pairs and free dislocations
are not observed. A Landau theory-based analysis is presented showing how a
strong local modulation may produce only a weak long range effect on the CDW
phase.
