The present disclosure relates to compositions comprising a hydrogel particle with optical properties substantially similar to the optical properties of a target cell, and methods for their use. Once the directory entry has been found, it may be immediately called through use of translated addresses assigned to the selected called party device. As a result, it is possible to improve the workability of the user of the present display system. Each element of the matrix has a value \u03c0i,j representing a weighted frequency of transition events from a first respective grade value to a second respective grade value divided by a weighted frequency of transition events initiating from the first respective grade value, so that the matrix successively approximates the road grade of the region.