If an object to be observed is much larger than the field of vision, we should observe it part by part as in the case of eye fundus photographs or gastrocamera photographs. Subpictures obtained through partial observation should be assembled into a mosaic picture which shows the whole object. An arrangement graph which shows adjacency and spatial differences among subpictures is defined, and the properties of the arrangement graph are discussed. Furthermore, the condition of the arrangement graph for a mosaic picture to be defect-free, that for a subpicture to be redundant in a mosaic picture, and the way to find subpictures surrounding defect areas of a mosaic picture are shown. The discussion is based on a graph theory and a notion of space vectors.