In the context of computer science, an index is a data structure that enables the efficient retrieval of specific items from a collection of data. An image database is a collection of digitized map images, with relevant objects or features represented by symbols. One search method for such a database is to determine the set of images that contain a desired arrangement of symbols. Examples are presented of index data structures to support the position-independent search of an image database, where the absolute positions of the symbols within the image are unimportant, and only the relative spatial relationships of the symbols are significant. By separating the size, shape, and orientation attributes of an arrangement, these index structures support efficient searching that is either size-dependent or size-independent, and either orientation-dependent or orientation-independent. The visual language of an existing retrieval-by-content image database system is extended to allow intuitive control of the additional search flexibility.